23

Logic II 23

any definite value, but (being, as we are supposing, devoid of skill,) would have to grind away blindly,
trying his weight every time he had ground off about as much
as the whole range of variation which he proposed to allow
himself. If he always ground off precisely the same amounts
between successive tryings of his weight, he would be just as
likely to grind below his maximum by any one fraction of
the amount taken off at a grinding as by any other; so that
his error curve woud be a horizontal line cut off by
vertical ordinates; thus [diagram]. But since there would be
a variability in the amount taken off between the trials, the
left hand side of the curve would show a sorted [moulding?]
with a contracy flexure, this: [diagram].
[marginal insertion:] It must be admitted that the distribution of Petrie's kets is suggestive
of this sort of curve, or rather or a modification of it due to a middling degree of skill.

Final Causation

I hope that long digression, (which will be referred to with
some interest when we come to study the theory of errors) will not
have caused the reader to forget that we were engaged in tracing out some
of the consequences of understanding the term "natural" or "real" class to mean
a class the existence of whose members is due to a common and peculiar
final cause. It is, as I was saying, a wide-spread error to think
that a "final cause" is necessarily a purpose. A purpose is