One example. Professor J.D. Bernal, a first-rank scientist, helped lay the foundations of molecular biology. Inspired by Nikolai Bukharin's lecture on the Marxist roots of Newton, he had earlier endorsed the "proletarian science" of Trofim Lysenko, whose theory of plant genetics Stalin backed because it suggested that the acquired characteristics of the communist New Man could be transmitted in perpetuity. Bukharin was later shot in the show trials of 1938 after torture extracted a confession; Bernal survived till 1971, when he died peacefully, proud of his Stalin Prize, and with no confession. 

As we contemplate the utopian claims of some branches of scientific inquiry today, the damage he and a generation of sympathisers and fellow travellers (including Joseph Needham, and to a lesser extent C.P. Snow) did to the reputation of science itself should not be forgotten. 

All this comes to mind as I try to keep abreast of neuroscience. I am not saying this is the new Marxism, merely that experiments and theories that claim to revolutionise our understanding of ourselves deserve the common reader's vigilance. Remarkable research is under way, but some in the neuroscience fraternity are not content with reinterpreting the world: they want to change it. "The return of political scientism, particularly of a biological variety," Raymond Tallis has written, "should strike a chill to the heart." It does to mine. Today Orwell's Animal Farm would feature a cold-eyed, white-coated meerkat loading troublesome creatures into a brain scanner, before prescribing the necessary treatment.

A new and precocious discipline, functional magnetic resonance imaging, fMRI, is a mere two decades old. Some of its triumphs, such as the ability to communicate with paralysed, "locked-in" patients, are impressive, and more will come. But to judge by highly-qualified critics like Tallis a Johnsonian bottom of common sense can be rare in the field.

The problem is that many neuroscientists are materialists and reductionists for whom it is axiomatic that man is no more than an animal with a more evolved brain: mind, consciousness and religion are figments of his intemperate imagination. The brain is the man and that is that — which handily shuts off competing explanations. Soon, we are told, we shall be able to read our own thoughts, motives, sexual desires or social behaviour so accurately, and to prescribe remedies so radical, that we can look forward to "a millennial future, perhaps only a few decades away". (Law and the Brain, by Semir Zeki and Oliver Goodenough, OUP, 2006.)