We need to know enough about the economics of an asset to make a reasonable estimate of its fair value, but although the critical aspects of an investment idea are often few in number, they tend to be difficult to quantify. Sound judgement is typically more important than supreme numerical modelling skills. Sometimes in-depth fundamental research gives one an edge on the market; often one’s advantage is purely behavioural. And in many instances the ability to take a longer-term view, free from short-term psychological pressures, makes the difference between implementing sensible investment ideas and idly standing by while the market delivers an exceptional opportunity. Understanding the nature of one’s edge on the market in any given investment idea is key. Without this understanding, investing is little more than a guessing game. And that is no way to go about compounding the capital of one’s partners.