Robert Nozick, who recently died aged 63, was one of the great philosophers of our day. In his 1974 classic, Anarchy, State and Utopia, he defended the justice of free enterprise and the sanctity of private property. The state, he argued, had no right to regulate "capitalist acts between consenting adults". And the attempt to redistribute wealth was no better than theft. To take, by force of law, Peter's earnings to subsidise Paul's is to reduce the former to the status of part-time slave labourer. Libertarians and right-wingers, to Nozick's delight and occasional discomfort respectively, took the book as a beacon. Probably few were converted by his arguments, but many were grateful for a rationale with which to decorate their prejudices.
Many of his students would say that in his 1981 work, Philosophical Explanations, Nozick actually solved a philosophical problem. Plato had argued that to "know" something meant being able to produce good reasons for holding our beliefs. Our limited powers of self-justification were the source of much trouble for philosophers thereafter. Nozick, however, argued that knowledge was an intimate but in effect blind relationship with the truth - the condition being, in a nutshell, that you would not have held a certain belief had it not been true. This presents an answer to the demon that challenged Descartes - the problem that we cannot know for certain that the world is not an illusion, that all we perceive is not merely a film set fabricated by a malicious genie. Under Nozick's theory, one could have knowledge of many things without necessarily being aware of the means by which one knows them. We may feel less than certain, but the point is that our feelings are irrelevant.
The acclaim Nozick received for this conclusion is ironic, as solutions were not generally his style. He was a philosopher who made tentative suggestions, positing possible solutions to problems rather than arguing the merits of one to the detriment of others. In his most recent and, sadly, last book, Invariances, the absence of strict proof for his contentions is excused by recourse to the workings of the sciences they feed off, in which theorists wait for experimentation to catch up with their inspired guesswork. The science he draws on most of all is evolution. He suggests, for example, that historical, or prehistorical, biases for one kind of truth over another are bound to be important to any creatures as sophisticated as our own species: "Must uncontaminated science be done only by amoebae?" Bias, for Nozick, is a labour-saving device that aids survival by ensuring that we do not have to learn how to see the world anew with every generation.
The same insights are employed against the question of why the laws of nature operate the way they do. This is the occasion for one of several blasts of pop science as compelling as anything found in Stephen Hawking's recent book. Nozick explores the physicist Lee Smolin's theory of evolutionary cosmology, which views physical laws as the heritable structure of a universe - akin to what in biology would be an organism's genetic endowment. These are passed on to the new universes that supposedly bubble off in the depths of black holes. Thus our universe might not be the best of all possible worlds, but it is at least one of the fittest. If the laws of its parents were not stable enough for them to mature to "reproductive age" (whereupon they produce black holes), the world in which we live would not exist. This may not be the kind of answer some people were looking for. It recalls the notorious attempt to account for the existence of human beings by saying that if the laws of nature were not such as to allow for our arrival on the scene, we would not be here to ask the question. This is like someone asking how they survived a car crash and being told that if they had died, they would not be around to examine their good fortune.
Taking a lead from science in this way is currently very popular among philosophers. It was, after all, their subject that spawned the likes of physics, biology and economics. Yet only quite recently have they taken an interest in how their progeny have fared. The need for new material and an envy of the laboratory's bright lights and big grants have demanded it. However, it is curious that the evolutionary science in particular that so obsesses many of today's thinkers does not owe its provenance to a school of philosophy. Philosophy, it seems, has asked to be looked after in its old age by other people's children.
Nicholas Fearn is the author of Zeno and the Tortoise: how to think like a philosopher (Atlantic Books)