Discussing robot consciousness in my last piece doesnotexist, in comments kindly points to a eulogy written by Frederick the Great on the French doctor and philosopher La Mettrie, whose little book "L'Homme Machine" is one of the earliest statements of full-blown materialism from the Enlightenment. Following his links gave me a really fascinating morning. Thanks.

Much of the rhetoric of "L'Homme Machine" could be cut and pasted into flame wars today:

"Experience and observation should … be our only guides ... Both are to be found throughout the records of the physicians who were philosophers, and not in the works of the philosophers who were not physicians. … Only the physicians have a right to speak on this subject. What could the others, especially the theologians, have to say? Is it not ridiculous to hear them shamelessly coming to conclusions about a subject concerning which they have had no means of knowing anything?"

This sounds the authentic note of the angry nerd down to this day. The arrogance and pugnacity that distinguished his character ring out with a wonderfully contemporary note:

"One can and one even ought to admire all these fine geniuses in their most useless works, such men as Descartes, Malebranche, Leibnitz, Wolff and the rest, but what profit, I ask, has any one gained from their profound meditations, and from all their works?"

La Mettrie wrote with authority as one of the leading doctors of his age. He never lacked for patients, and indeed died after overeating at a banquet thrown for him by a nobleman he had cured. He studied under the great Dutchman, Hermann Boerhaave (with whom Linneaus also studied). Nils-Erik Landell, one of Linnaeus's biographers, says that no doctor before or since has ever been more famous in Europe than Boerhaave.

It is unfortunate that most of what they all believed, and taught, was nonsense. A flavour of La Mettrie's attitude comes through his treatment of delusions:

"Why should I stop to speak of the man who imagines that his nose or some other member is of glass? The way to help this man to regain his faculties and his own flesh-and-blood nose is to advise him to sleep on hay, lest he beak the fragile organ, and then to set fire to the hay that he may be afraid of being burned - a fear which has sometimes cured paralysis."

If it didn't, presumably the patient was in no condition to complain, nor his surviving relatives to sue.

Boerhaave believed that fevers were caused by a build up of slime in the blood. Linnaeus made his name as a doctor in Stockholm by prescribing a bottle of hock a day as a treatment for syphilis to the young cavalry officers stationed there.

But the prestige of doctors is curiously unaffected by their lack of success. Until around 1900, we now know, the medical profession scarcely cured anyone and did nothing to increase average life expectancy. Without a correct theory of disease it could not hope to discover remedies except by chance. Yet faith in doctors, and the belief that their endeavours were scientific, remained almost entirely unaffected by these distressing facts. It's a point that would be well worth bearing in mind by the people who now campaign against homoeopathy and even faith healing – I don't mean that modern medicine is no more effective than the old sort, because it clearly is; but that the prestige of a project can survive any amount of failure so long as no alternatives are readily available.