Health and Disease 
Medawar: If vitalism is such a valuable method of thinking, 
would you give us a valuable thought? 
Klein: I don’t say that vitalism is a valuable way of thinking, 
but I am quite sure that in all that we are doing in human 
biology, we cannot work with physical and chemical models 
alone. 
MacKay: In saying this, surely you are saying something 
which would also be true of engineering? The change from 
discussing the action of force on force to discussing the action 
of form on form is characteristic of any change from a pure to 
an applied science. It characterizes our way of talking about 
both living and non-living teleological (cybernetic) mecha- 
nisms. 
Klein: Teleology is akin to vitalism. 
MacKay: But cybernetics typically reinstates teleological 
forms of thought without denying the adequacy of physical 
explanation at its own level. This is why so many of us don’t 
like the term vitalism. Vitalism is not a positive term for most 
people but a negative one; it stands for a “postulate of im- 
potence”’ at the physical level. There is no postulate of impo- 
tence involved in accepting the cybernetic way of describing a 
living system. It implies, not that explanation at the physical 
level is impossible, but merely that it misses the point revealed 
in teleological terms. 
Klein: The man who fought vitalism hardest was Claude 
Bernard, and once he had finished fighting vitalism he brought 
in the idée directrice and the milieu intérieur. 
Huxley: MacKay used the word teleological. I would prefer 
him to use the word teleonomic which was introduced into 
biology a few years ago. This does not imply, as the term tele- 
ological usually does, that there must be a conscious purpose 
behind evolution, but that it is automatically, or if you like, 
homoeostatically, directed to some functional end. 
Comfort: Perhaps the model that Dr. MacKay was looking 
for was the thing which was worrying Dr. Szent-Gy6rgyi about 
the coincidence of successive mutations. I believe some work 
has been done on the analogy of the anagram where you start 
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