An anti-thesis is written in advance and costs nothing to write, which is exactly why it works when the attractive version of the thing you swore off finally shows up.
9 min read · Level 2
The entries that earn their place are almost never the exotic ones. Nobody needs a written rule to avoid the thing they find obviously foolish - the list does no work there, because the temptation was never present. The entries that matter are the ones sitting immediately next to what you actually do: the adjacent sector, the slightly longer lock-up, the business that looks like the ones you understand but turns on a risk you cannot price. Those are the ones that will arrive wrapped in a warm introduction from somebody whose judgement you rate, at a moment when the fit is 80% and the missing 20% is precisely the part you cannot evaluate. I would argue that an anti-thesis containing nothing uncomfortable to enforce has not been written honestly, because the whole instrument exists for the case where you can feel yourself wanting to make an exception. If reading your own list never annoys you, it is describing your habits rather than constraining them.
An anti-thesis is the written list of things you have decided you will not invest in, and why. It is not a list of things you dislike. It is a list of categories where you have concluded - calmly, in advance, with reasons - that you are unlikely to do well, and where you are therefore pre-committing to decline regardless of how good the specific opportunity looks.
The reasons tend to fall into four groups:
No edge You have no way to know more than the average buyer Wrong shape The return profile does not fit how you actually behave Cannot monitor You would not be able to tell how it was going Values You have decided you do not want to own it, and that is sufficient
The fourth is worth stating plainly because people feel they need a financial reason for it. They do not. An anti-thesis is allowed to contain "I do not want to" as a complete entry.
What makes the list work is when it is written. Any category looks avoidable in the abstract and every category looks compelling in the form of one specific, well-presented opportunity brought to you by someone you like. The abstract moment is the only one where your judgement is uncontaminated, so it is the moment that should bind.
A usable entry has three parts:
The category narrow enough to recognise when it arrives The reason why you do not expect to do well, in your own words The exception what, if anything, would legitimately change this
The exception clause is what keeps the list from being dogma. Written in advance, it is a genuine condition - "unless I have spent a year working in the sector" or "unless somebody I trust with direct operating experience is investing alongside and will do the monitoring". Invented in the moment, in the presence of an attractive opportunity, it is a rationalisation, and you will not be able to tell the difference from the inside. That is the whole reason it is written down early.
Because saying no is expensive in ways that have nothing to do with money. It is socially awkward, it is often wrong in hindsight, it produces no story, and it requires you to disappoint somebody in the room. The anti-thesis moves that cost from the meeting, where it is highest, to a quiet afternoon, where it is nearly zero.
It also solves a problem a positive thesis cannot. A thesis tells you what fits. It is silent about the opportunity that fits beautifully and sits in a category where you have no business operating - the fintech thesis applied to a lending business you cannot underwrite, the software thesis applied to a company whose real risk is clinical. Those are the ones that get through, because they pass the test you were applying.
And it protects the thing a portfolio actually runs on, which is attention. Every opportunity considered seriously costs hours that are not available to anything else. An investor who will consider anything has, in practice, no time to do proper work on the things they are best placed to judge. The list is not just a defence against bad investments; it is what makes good ones affordable.
Educational, not personalised financial advice. Nothing in the Investor Academy is a recommendation to buy, sell or hold anything — what is right for you depends on your own circumstances and the rules where you live.
An investor writes four entries at the start of a year, before any of them is live.
Category Reason Exception Early-stage biotech Cannot evaluate a clinical claim, and the A qualified scientific outcome turns on one, so my judgement adds partner does the technical nothing to the price I would pay work and co-invests Anything with a lock-up Have twice needed liquidity sooner than None. Twice is a pattern beyond five years expected and sold badly to get it Consumer hardware Cannot monitor inventory or supply chains Direct operating experience from outside, so I would learn of problems on the team I can call a quarter after the founder does Businesses whose revenue Do not want to own it None depends on gambling
What happened in March. A hardware company arrives through a trusted introduction. The product is genuinely excellent, the founder is impressive, the round is oversubscribed, and two investors the person respects are in. Every instinct says yes.
The list says: cannot monitor inventory or supply chains from outside. The exception is direct operating experience on the team the investor can call. There is none. They decline in a day, write two sentences explaining exactly why, and offer an introduction to someone better placed to judge it.
The part that matters. The company did well. The investor missed a good outcome, and their reasoning was still correct - because the question was never whether this company would succeed, it was whether they could tell in advance which hardware companies would, and whether they could tell in time if this one stopped working. They still cannot. Had they invested and done well, they would have learned the wrong lesson and taken three more.
The part that is easy to miss. Declining in a day rather than over five weeks left five weeks for two opportunities inside the thesis, one of which they took. The anti-thesis is usually sold as protection from losses. Most of what it actually buys is time.
Treating an anti-thesis entry as a rule that a sufficiently good opportunity can override. If a good enough opportunity suspends the rule, there is no rule - because every opportunity that reaches you will arrive looking like the exception, presented by someone persuasive, at a moment when declining feels needlessly rigid. The list either binds when it is inconvenient, which is the only time it can bind, or it is a list of preferences you have written down.
Look for the reason underneath the stated one. If three of five were declined because you could not judge something technical, that is an anti-thesis entry you already hold without having written it. Starting from your own behaviour produces a more honest list than starting from principles.
One bad outcome is a data point and may be luck. The same mistake twice, in the same shape, is a pattern about you rather than about the asset. Those are the highest-value entries because they are the ones your future self will be most confident are behind them.
For each entry, state what would legitimately change the decision, or write "none" and mean it. Doing this in advance is what separates a real condition from a rationalisation, because you are writing it when no attractive opportunity is in the room to bend it.
A list in a document you open twice a year does nothing. Put it where you record opportunities, so it is read at intake rather than recalled at decision time, and date every amendment so drift is visible.
Write it when nothing is live, review it once a year, and read it at the moment an opportunity arrives rather than at the moment you decide. It is most valuable for investors with good deal flow, because the constraint there is attention rather than opportunity, and for anyone whose network is concentrated in a field they are not themselves expert in.
Do not let the list grow until it excludes everything unfamiliar, because then it has stopped being an anti-thesis and become a description of your comfort zone with reasons attached. The test is whether each entry names a specific reason you would do badly rather than simply the absence of experience. Everything is unfamiliar before it is not, and an investor who never enters a new category will slowly be left holding only what they understood a decade ago.
An investor decides they will not invest directly in a category they cannot judge - commonly early-stage biotech or hardware. Some months later they commit to a specialist fund covering exactly that category, on the reasoning that the manager has the expertise they lack. Often this is sound, and it is precisely what the exception clause anticipates. But it frequently happens without the entry being consulted at all, and so the questions the entry would have forced - can I evaluate this manager any better than I could evaluate the underlying companies, and will I be able to tell how it is going - go unasked. The exposure returns through a door nobody thought to check.
Read the anti-thesis at fund and syndicate intake too, not only for direct opportunities. The reason for the entry usually applies to the exposure however it is wrapped.
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