I think of myself as a Marxist – in much the same sense as I think of myself as a Darwinian, a Freudian, a Newtonian, etc. These guys were all brilliant and remain, always will remain, indispensable.

But none of these theories is a Theory of Everything. Freud doesn’t even try, but the others have been badly abused by their admirers. Darwin becomes sociobiology, Newton becomes the Clockwork Universe, and Marx – well, Marx is the burden of my song.

Let’s step back for a moment. All good theories have a scale at which they apply. Newtonian mechanics is really good for predicting, say, the trajectory of a comet, just from one or two observations, or the motions of the planets. It’s not good at predicting, or explaining, the shape of the little whirlpool in your bathtub drain, or the weather, or the movement of dust motes in the late-afternoon sunbeam shining palely through your wintry window.

Freud gives us a good, or at least highly suggestive, account of how neurosis happens. He can’t explain in principle why Sam becomes neurotic and Steve doesn’t, even if their life histories are very similar – though as a clinical practitioner he might suss it out, if they both came to him for analysis. This doesn’t mean he was wrong, you understand; it just means that a theory describes phenomena at some particular level of scale, or of generality, and not above or below it.

Darwin gives us a general theory of how organisms evolve, and no reasonable person thinks he was wrong; but notoriously, the theory of evolution throws up its hands in particular cases, except for brilliantly obvious ones like Darwin’s dear little finches. Evolution is the explanatory framework for things like the development of the eye but doesn’t explain it, in any substantive way. An explanation would involve setting out the steps – it would be, in fact, a closely connected narrative – and we don’t have that and never will, probably.

Which brings me to our man Marx.

Too many Marxists want Marxism to be a theory of everything. Brilliant as Dr Marx was, this is asking too much of him. As with Darwin, our great man provides an explanatory framework for certain aspects of human history (and not for others; I’m not aware that he tried to explain Grimm’s Law). If our man is right, and I think he is, then every actual particular explanation needs to fall within its ambit – no lusus naturae, please. But at the smaller level of scale, Big Theory doesn’t apply. That’s not to say Big Theory is wrong, or has failed; it’s to say that Big Theory is talking about something else.

Marxism doesn’t explain why Capitalist A fails and Capitalist B becomes Jeff Bezos. Doesn’t try to. Marx leaves plenty of scope for the chapter of accidents, the random event, the butterfly’s wingflap that causes the hurricane.

Years ago, when I was trying to make sense of the First Transition – from late antiquity to feudalism, in Europe – I was very puzzled about why the Visigoths became Arians rather than orthodox Christians. There must be a reason, surely? Doesn’t Marx shed some light on this?

I mentioned this perplex to a seasoned old mediaeval historian. His response: “Well, the Arian missionaries got to them first, I guess.”

Chapter of accidents; too small-scale for a Big Theory explanation. We need to keep this idea in mind.