The Most Important Thing: Uncommon Sense for the Thoughtful Investor
The title is deliberately ironic. There isn’t one most important thing. There are perhaps twenty, and Marks works through all of them with the patient thoroughness of someone who learned each lesson the hard way. The book is built around a series of memos Marks wrote to Oaktree Capital Management’s clients over the years — analytical frameworks developed in real time while navigating real markets, not theories constructed in retrospect to explain outcomes already known. That gives the book an unusual texture: it reads like thinking in progress rather than a conclusion already reached, which makes it more valuable as a guide to the process of investing than as a catalog of results.
The “Illuminated Edition,” expanded with commentary from peers including Joel Greenblatt, Seth Klarman, Christopher Davis, and Paul Johnson, adds another layer of value by showing how these frameworks land with serious practitioners. Their marginal comments — sometimes endorsing Marks’ points, sometimes pushing back, sometimes extending them — turn the book into a conversation rather than a lecture, and make the frameworks more vivid by showing how they’ve been applied and tested.
Second-Level Thinking
The concept running through every other idea in the book is what Marks calls “second-level thinking.” First-level thinking is simple, superficial, and common: “This is a good company; therefore I should buy the stock.” “The economy is weakening; I should sell.” “This company’s earnings will grow; the stock should go up.” First-level thinking produces average results at best, because first-level insights are available to everyone — they’re already reflected in current prices.
Second-level thinking is more complex, more contrarian, harder to execute: “This is a good company, but everyone already knows it’s a good company, so the stock is fully priced and I shouldn’t pay up.” “The economy is weakening, but everyone expects it to weaken, and that negative expectation is already reflected in depressed stock prices, which means stocks may actually be a buy.” “This company’s earnings will grow, but not as fast as the market expects, which means the stock will disappoint relative to consensus and may fall despite good earnings.” Second-level thinking is about understanding not just the reality but the gap between reality and expectations — because that gap is where investment returns come from.
Deceptively simple, genuinely revolutionary. Most investment discussions focus on analyzing fundamentals — the quality of the business, the competence of management, the prospects for growth. These things matter, but they’re not the whole story. The price paid matters equally, and the price reflects a set of expectations that may or may not be correct. The investor who buys a great business at a price that fully reflects its greatness hasn’t done anything clever — she’s just paid for what she’s getting. The investor who buys an average business at a price that significantly underestimates its prospects has done something genuinely intelligent, regardless of how the business compares to the great one on any fundamental metric.
Marks emphasizes that second-level thinking requires having a view that differs from consensus AND being right when the consensus is wrong. Both conditions are necessary. Plenty of investors hold different views from consensus — contrarianism for its own sake is easy. Fewer are systematically right when consensus is wrong, because consensus often reflects genuine information and genuine wisdom. The sophisticated investor’s job is identifying the specific cases where consensus is systematically wrong — where collective psychology has driven prices away from fundamental value in a direction careful analysis can exploit.
The Role of Risk
Marks’ treatment of risk is among the most penetrating in the investment-book canon. He argues that the conventional financial definition of risk — the volatility or standard deviation of returns — isn’t what risk actually means to intelligent investors. Volatility is observable and measurable, which makes it amenable to mathematical treatment, but it’s not the same thing as the risk of permanent capital loss, which is what investors actually care about.
The risk that matters is the probability that an investment produces results well below expectations, or results in significant permanent loss of capital. Forward-looking, subjective, not directly observable from past price behavior. A stock that’s been very stable in price might be extremely risky if it’s trading at a price that assumes unrealistically optimistic outcomes. A stock that’s been highly volatile might be relatively safe if it’s trading at a price with significant margin for error already built in.
Marks makes the counterintuitive but important point that risk and return are not the simple linear relationship financial theory assumes. Yes, investments with higher prospective returns generally require taking higher risks — that’s the fundamental principle. But the relationship is probabilistic rather than deterministic. Higher-risk investments don’t reliably produce higher returns; they produce a wider range of outcomes, some very good and some very bad. The skilled investor’s job isn’t maximizing expected return for a given level of risk — it’s finding opportunities where the risk/return tradeoff skews favorably, where the potential upside is significantly greater than the potential downside.
Which is why Marks emphasizes what he calls “asymmetric” return profiles — investments where you win a lot if things go well and lose a little if they don’t, rather than investments where you win a little if things go well and lose a lot if they don’t. The asymmetry comes partly from price — buying at a price significantly below intrinsic value creates a natural asymmetry — and partly from the structure of the investment itself. Distressed debt, which Oaktree specializes in, has a natural asymmetric profile: the most you can lose is what you paid, but if the company recovers, the upside can run to multiples.
Marks also distinguishes between risk-taking that’s consciously chosen and understood versus risk-taking that’s unconscious or concealed. The investor taking significant equity risk while believing she’s taking modest bond risk isn’t brave — she’s confused. The investor concentrated in a single sector while believing she’s diversified hasn’t taken calculated risk; she’s made an error. Genuine risk management requires honest assessment of the actual risk being taken, which requires both analytical skill and the self-awareness to notice when motivated reasoning is distorting that assessment.
Understanding Market Cycles
Marks identifies the fundamental driver of cycles as the pendulum swing in investor psychology. Markets don’t move randomly. They move in response to shifts in collective psychology — the shift between fear and greed, risk aversion and risk appetite, skepticism and credulity. When markets are rising and investors are doing well, risk tolerance increases, standards for analysis decline, and capital flows into increasingly speculative opportunities. When markets fall and investors are losing money, risk aversion spikes, even genuinely attractive opportunities get shunned, and capital retreats to government bonds regardless of the relative value on offer elsewhere.
The skilled investor’s job is maintaining an approximate sense of where things stand in these cycles — not predicting specific turning points, which is impossible, but assessing whether aggregate investor psychology leans toward fear or greed, whether analytical standards are rising or falling, whether credit conditions are tight or loose. These aggregate assessments inform positioning: more aggressive when fear dominates and prices are depressed, more defensive when greed dominates and prices are elevated.
Marks develops this into what he calls “market temperature” — a set of observable indicators pointing roughly to where collective psychology sits at any given time. What are people talking about? Worried about losing money or eager to make it? Are credit markets tight or loose? Are new, exotic instruments being invented to give investors access to yield they can’t find in conventional markets? Are famous investors confident or cautious? Are investment banks building increasingly complex products to satisfy demand for returns? No single indicator is definitive. Together, they paint a picture of aggregate sentiment genuinely useful for portfolio positioning.
The late stages of a credit cycle have distinctive fingerprints Marks describes in careful detail: covenant-lite loans, PIK (payment in kind) bonds, exotic structured products, unprecedented deal structures, and — the surest signal — widespread rationalization of why historical standards of creditworthiness no longer apply. He was writing about these signals in 2006 and 2007, and his memos from that period demonstrate the value of the cycle-aware framework: while most market participants were still generating strong returns and dismissing concerns about credit quality, Marks was flagging the late-cycle indicators that presaged the 2008 crisis.
The Investor’s Dilemma: Survival vs. Maximization
Marks draws a distinction that’s simple but important: most investment frameworks are designed to maximize returns, but the first requirement of successful long-term investing is survival — avoiding the catastrophic losses that stop compounding from working. These goals aren’t always in conflict, but they often are, and when they conflict, survival has to win.
Easier to state than to honor, because the psychological pressure in bull markets always runs toward maximizing returns. The investor holding defensive positions while markets rise looks foolish to clients comparing her returns to peers fully invested in appreciating assets. The pressure to “stay relevant” and “not miss the rally” is enormous, and it drives intelligent, experienced investors to abandon prudent risk management at exactly the point in the cycle when prudent risk management matters most.
Marks cites Buffett’s famous rules — “Rule #1: Never lose money. Rule #2: Never forget Rule #1” — not as a literal injunction against any investment that goes down, but as a statement about priorities. Avoiding major losses is more important than capturing every gain, because the mathematics of drawdowns is brutal: a 50% loss requires a 100% gain just to break even, and the compounding time lost during recovery is irreplaceable. The patient, defensive investor who gives up some upside in bull markets but avoids major drawdowns in bear markets will almost always outperform the aggressive investor who captures every upswing but suffers every crash.
This survival-first orientation also explains Marks’ emphasis on “good defense” — portfolio construction built primarily to avoid large losses rather than to maximize expected returns. Good defense means meaningful diversification, avoidance of excessive use, maintenance of liquidity reserves, and honest stress-testing against adverse scenarios. None of it produces the best returns in good times. It produces the best outcomes over full market cycles — the only time frame that actually matters.
Price Relative to Value
Most importantly, he emphasizes that intrinsic value is not a precise number — it’s a range, and it can be quite wide depending on the uncertainty about future cash flows, the appropriate discount rate, and the competitive dynamics of the business. The investor claiming to know the exact intrinsic value of a complex business is probably deceiving herself. The investor who can estimate a reasonable range and then buy only when the market price sits substantially below the bottom of it is operating intelligently.
This is the essence of the margin of safety concept, which Marks credits to Graham but applies with his own characteristic emphasis on psychological discipline. The margin of safety protects against more than analytical errors — it protects against the inherent uncertainty of the future. Even correct analysis of business fundamentals will get surprised: the economy will do something unexpected, a competitor will move in a way that wasn’t anticipated, management will make a decision that changes the business’s economics. The margin of safety cushions against those inevitable surprises.
Marks is also careful to distinguish cheapness from value. A stock down 50% is not necessarily cheap — it may have fallen because the business genuinely deteriorated, and the current price may still sit above intrinsic value. Cheapness is relative, and it requires an independent estimate of intrinsic value as the reference point. Sounds obvious. But the failure to make this distinction accounts for a significant share of value traps — investments in stocks that look statistically cheap but are cheap for fundamental reasons the investor failed to properly analyze.
The Importance of Knowing What You Don’t Know
Marks is deeply skeptical of macro forecasting — predicting economic conditions, interest rates, exchange rates, and other macro variables as inputs to investment decisions. Not because these things don’t matter, but because the evidence that anyone can reliably forecast them is thin, and the evidence that people believe they can is overwhelming. The gap between the confidence macro forecasts are made with and the accuracy they’re borne out with is one of the most consistent findings in financial history.
Which leads to one of his most important practical prescriptions: build portfolios that can do reasonably well across a range of macro scenarios rather than ones optimized for a single forecast. The investor who says “I believe interest rates will rise, so I’m positioning the entire portfolio defensively” is making a very strong bet on a forecast that’s almost certainly partially wrong. The investor who says “I don’t know whether rates will rise or fall, but I want to own assets cheap enough to do well across multiple scenarios” is being more honest about uncertainty, and stronger in portfolio construction as a result.
This epistemic humility isn’t passivity — Marks isn’t arguing for index funds or random portfolio construction. He’s arguing that the bets taken should rest on things that can actually be analyzed with confidence — individual company fundamentals, relative valuation, aggregate market psychology — rather than on macro predictions where confidence significantly exceeds competence.
The distinction between “I know what will happen” and “I know something about probabilities” is important here. Marks doesn’t claim to know what will happen — nobody does. What he claims is the ability to assess whether probabilities skew favorably or unfavorably, and to position accordingly. This probabilistic thinking — accepting uncertainty while still making calibrated assessments of relative probability — is a more honest and more practically useful framework than the deterministic predictions most market commentary pretends to offer.
Contrarianism and Its Limits
Marks formulates this as a two-question test: First, what’s the consensus view? Second, is there reason to believe the consensus is wrong? If yes — genuine analytical insight the consensus is missing, crowd judgment driven more by emotion than analysis, a price implied by the consensus extreme enough to suggest irrational exuberance or panic — contrarianism is warranted. If the consensus rests on solid analysis and there’s no compelling reason to think it’s wrong, the contrarian bet isn’t brave. It’s just different for its own sake.
Second-level thinking is important here. The contrarian investor isn’t trying to be different. She’s trying to be right. Sometimes that means agreeing with consensus; sometimes disagreeing. The discipline is in the quality of the analysis, not the direction of the conclusion.
Marks is particularly clear about the asymmetric cost of being wrong at the extremes versus the middle of the cycle. Being slightly too early reducing risk at the top of a cycle costs some upside. Being complacent at the top and then forced to de-risk at the bottom after a major drawdown can permanently impair a portfolio. That asymmetry — mistakes at extremes far more costly than mistakes in the middle — is the strongest argument for cycle-aware portfolio positioning, even if timing the exact top or bottom is impossible.
The Psychological Demands of Investment
Marks devotes considerable attention to the psychological demands of investment — the emotional disciplines required to run a rational strategy in the face of market volatility, peer pressure, and the constant temptation to react to short-term noise. He’s particularly pointed about the difficulty of holding conviction in unpopular positions.
The most important investments — the ones generating extraordinary long-term returns — are almost always uncomfortable. Uncomfortable because they’re contrarian: buying assets other investors are selling in panic, holding through periods of significant paper losses, avoiding assets generating spectacular returns for everyone else. Each action requires overriding a powerful cognitive and emotional impulse. The impulse to stop the pain of paper losses. The impulse to follow the crowd into what appears to be working.
The impulse to take profits when available rather than sit with uncertainty.
Marks argues that developing what he calls “psychological edge” — the capacity to act rationally when market conditions make rationality uncomfortable — matters as much as any analytical skill. The investor with better quantitative models than everyone else who abandons her convictions under pressure will underperform the investor with mediocre models who holds disciplined conviction through difficult periods. Which is why temperament, as Buffett has often said, matters more than intelligence in investing.
The idea that “being early is the same as being wrong” is one Marks addresses directly and honestly. Buy an asset at what looks like a fair price, and it keeps falling for two more years before recovering — technically right in the analysis, practically painful to have held. Most investors can’t maintain the conviction to hold through that kind of extended underperformance, even when the fundamental analysis hasn’t changed. Building that conviction — through deep research, careful calibration of uncertainty, and an honest account of what would actually change one’s mind — is one of the most valuable investments an investor can make in her own process.
The Memo Methodology
The memos work because they’re written in real time, before outcomes are known. That forces Marks to reason under genuine uncertainty rather than construct post-hoc explanations for known outcomes. It also creates a public record of his thinking that subjects him to accountability — a 2006 memo flagging excessive risk appetite in credit markets and urging caution, confirmed by the 2008 crisis, is genuine evidence the framework was working. Had the memos repeatedly predicted crises that never materialized, the framework would need revision.
The book draws heavily on these memos and explains the thinking behind them, making it effectively a retrospective account of how second-level thinking has been applied in practice across multiple market cycles. Enormously more valuable than a theoretical account, because it shows both the conclusions and the reasoning process that generated them. The reader can evaluate not just whether the conclusions were correct but whether the reasoning process that produced them is one worth replicating.
Risk Control and Asymmetric Returns
Marks is unusual among investment writers for the sustained emphasis he places on the downside — on what happens when things go wrong. This reflects his background in credit investing, where the upside is capped (the most you get back is what was lent, plus interest) and the downside is open (everything can be lost). In that environment, rigorous attention to downside scenarios isn’t optional. It’s the foundational discipline of the business.
He argues that this credit investor’s mindset — systematically stress-testing every investment against adverse scenarios before committing capital — is actually the right framework for all investing, not just credit. Equity investors focused only on upside scenarios are systematically underweighting the probability of bad outcomes and building portfolios more fragile than they appreciate. The equity investor who asks “what’s the worst case here, and can I live with it?” before every investment is applying a discipline that protects against the catastrophic losses that destroy long-term returns.
The goal isn’t avoiding all risk — risk and return are inseparable, and trying to avoid all risk produces returns too low to be useful. The goal is taking risks that are consciously chosen, accurately assessed, and appropriately compensated. Which requires the discipline to say no to many apparently attractive opportunities because the downside analysis doesn’t support the commitment — one of the hardest things in investing and one of the most important.
Marks closes with an observation tying together everything in the book: the fundamental challenge of investing isn’t analytical. Anyone with adequate training can learn to value businesses. The fundamental challenge is behavioral — the discipline to buy when it’s scary, sell when it’s comfortable, maintain conviction through underperformance, and recognize one’s own limitations and errors. These behavioral skills get built through experience and honest self-examination, not through study alone. The book can describe the destination. Only practice gets you there.
The clinical takeaway
“The Most Important Thing” is one of the small number of investment books that will still be relevant fifty years from now. Not because it contains timeless truths about specific securities or sectors — no investment book does. But because it articulates a framework for thinking about investment that addresses the enduring realities of markets: that prices reflect expectations, that the gap between expectations and reality is where returns are made, that psychology drives prices away from value at both extremes, and that the investor’s primary challenge is to think clearly and act rationally when both are difficult.
Marks is a precise, disciplined writer, and the book is correspondingly precise and disciplined. It rewards careful reading and repeated returns as investment experience accumulates and gives the framework more resonance. The first time you read about second-level thinking, it sounds clever. The tenth time you encounter a situation where everyone in the market has arrived at the same obvious conclusion, and you ask yourself whether that obvious conclusion is already priced in — that’s when the framework becomes operational. That’s when books like this pay off.
Lessons from Oaktree’s Investment History
One of the most instructive aspects of “The Most Important Thing” is that Marks doesn’t just articulate principles — he illustrates them with Oaktree’s actual investment history across multiple cycles. The 2001-2002 telecom distressed cycle, the 2002-2007 used buyout boom, and the 2008-2009 global financial crisis all appear as case studies demonstrating the framework in action. Each case shows both the analytical judgment calls and the psychological challenges of implementing the framework under real conditions, with real money and real client relationships at stake.
The 2008-2009 period is particularly instructive. Marks describes the experience of deploying capital aggressively into distressed credit during the fourth quarter of 2008 — prices collapsing, bank failures occurring weekly, the prospect of complete financial system collapse seeming genuinely possible. The analytical case for buying was clear: high-quality bonds traded at prices implying default rates far in excess of any plausible scenario, even in a severe recession. But the emotional case required confronting genuinely terrifying macro uncertainty and overriding the fear response every rational market participant was experiencing simultaneously. The investors who bought in Q4 2008 and Q1 2009 generated extraordinary returns in the subsequent recovery. The investors who let fear dominate locked in losses at the worst possible prices.
Marks is clear that this kind of aggressive buying at distressed prices isn’t simple mechanical formula application — it requires genuine conviction about the range of likely outcomes, genuine comfort with the possibility of being early (and therefore losing more before recovering), and genuine organizational discipline to maintain the strategy when short-term results look terrible. Those requirements are why most investors, despite knowing the principle, fail to execute it when it matters most. The gap between knowing and doing is vast, and it’s entirely behavioral rather than analytical.
The book’s honest account of these experiences — including cases where Marks’ timing was wrong, where positions were too large, where the framework was correctly applied but the market stayed irrational longer than expected — gives it a credibility purely prescriptive texts lack. Marks has lived through the situations he describes, made the errors he acknowledges, and refined the framework through decades of real experience. That earned authority is what makes the advice worth following.
The Relationship Between Risk and Return Revisited
Marks returns to the risk-return relationship in the book’s final chapters with a subtlety easy to miss on first reading. The conventional view — higher risk produces higher returns — is both true and misleading. True in the sense that expected returns on riskier assets are higher than on safer ones, as compensation for bearing additional risk. Misleading in the sense that this higher expected return isn’t guaranteed. It’s the average outcome across a distribution of possible scenarios, and individual outcomes can diverge dramatically from the average.
Which matters because the investor taking additional risk to capture higher expected returns may or may not actually receive them, depending on which scenario materializes. The used investor who compounds at 15% in a benign environment and loses 60% in a crisis hasn’t earned the risk premium — she’s consumed it and then some. The unleveraged investor who compounds at 10% steadily across all environments may significantly outperform over a full cycle despite lower expected returns in any given one. The temporal distribution of returns, not just the average level, determines actual investor outcomes over a finite horizon.
This insight — that the sequence of returns matters as much as the average of returns — is one of the most practically important and most widely ignored in investment practice. Institutional frameworks that treat expected return and standard deviation as the complete description of an investment’s risk profile miss the important question of what happens when bad scenarios actually materialize, and whether the investor can survive and recover. Marks’ framework, which puts survival first and return maximization second, is more consistent with how actual long-term investment success gets achieved.
The takeaway for practical portfolio construction is clear: size positions to survive the worst plausible scenarios, not just the average one. Maintain the liquidity and financial flexibility to add to positions when prices are most attractive — which is when fear is greatest and prices lowest. And structure the process to take advantage of market cycles rather than be victimized by them. Not complicated prescriptions. Demanding ones, though, and their implementation requires both analytical rigor and behavioral discipline of a high order. The Most Important Thing is that you bring both.
Howard Marks has said that he writes his memos not to tell people what to think, but to show them how he thinks. That’s exactly right as a description of “The Most Important Thing.” A book about process — the frameworks, habits of mind, and psychological disciplines that lead to better investment outcomes over time. Whether the specific tactical conclusions Marks draws at any given moment turn out correct matters less than whether the reader internalizes the process well enough to draw her own correct conclusions when the next cycle brings its own distinctive pressures and opportunities. On that measure, this is among the most valuable investment books ever written.
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