ns and senses has much influence both on our metaphysics and our
morality." This, I may observe, does not in the least show that in a
society of human beings, not blind, but endowed with vision, the sense
of physical shame is a mere prejudice of which philosophy will rid us.
The fact that a blind man discerns no ill in nakedness, has no bearing
on the value or naturalness of shame among people with eyes. And
moreover, the fact that delicacy or shame is not a universal human
impulse, but is established, and its scope defined, by a varying
etiquette, does not in the least affect the utility or wisdom of such an
artificial establishment and definition. The grounds of delicacy, though
connected with the senses, are fixed by considerations that spring from
the social reason. It seems to be true, as Diderot says, that the
born-blind are at first without physical delicacy; because delicacy has
its root in the consciousness that we are observed, while the born-blind
are not conscious that they are observed. It is found that one of the
most important parts of their education is to impress this knowledge
upon them.[66]

But the artificiality of a moral acquisition is obviously no test of
its worth, nor of the reasons for preserving it. Diderot exclaims, "Ah,
madam, how different is the morality of a blind man from ours; and how
the morality of the deaf would differ from that of the blind; and if a
being should have a sense more than we have, how wofully imperfect would
he find our morality!" This is plainly a crude and erroneous way of
illustrating the important truth of the strict relativity of ethical
standards and maxims. Diderot speaks as if they were relative simply and
solely to our five wits, and would vary with them only. Everybody now
has learnt that morality depends not merely on the five wits, but on the
mental constitution within, and on the social conditions without. It is
to these rather than to the number of our senses, that moral ideas are
relative.

Passing over various other remarks, we come to those pages in the Letter
which apply the principle of relativity to the master-conception of God.
Diderot's argument on this point naturally drew keener attention than
the more disinterestedly scientific parts of his contribution. People
were not strongly agitated by the question whether a blind man who had
learned to distinguish a sphere from a cube by touch, would instantly
identify each of them if he received sight.[