young than when old--when hungry than when our appetite is satisfied--in
the night than in the day--when peevish than when cheerful. Thus,
varying every hour, by a thousand other circumstances, which keep us in
a state of perpetual inconstancy and instability." Every day may be seen
children, who, to a certain age--display a great deal of ingenuity, a
strong aptitude for the sciences, who finish by falling into stupidity.
Others may be observed, who, during their infancy, have shown
dispositions but little favourable to improvement, yet develope
themselves in the end, and astonish us by an exhibition of those
qualities of which we hardly thought them susceptible: there arrives a
moment in which the mind takes a spring, makes use of a multitude of
experience which it has amassed, without its having been perceived; and,
if I may be allowed the expression, without their own knowledge.

Thus, it cannot be too often repeated, all the ideas, all the notions,
all the modes of existence, and all the thoughts of man, are acquired.
His mind cannot act, cannot exercise itself, but upon that of which it
has knowledge; it can understand either well or ill, only those things
which it has previously felt. Such of his ideas that do not suppose some
exterior material object for their model, or one to which he is able to
relate them, which are therefore called _abstract ideas_, are only modes
in which his interior organ considers its own peculiar modifications, of
which it chooses some without respect to others. The words which he uses
to designate these ideas, such as _bounty, beauty, order, intelligence,
virtue_, &c. do not offer any one sense, if he does not relate them to,
or if he does not explain them by, those objects which his senses have
shewn him to be susceptible of those qualities, or of those modes of
existence, of that manner of acting, which is known to him. What is it
that points out to him the vague idea of _beauty_, if he does not attach
it to some object that has struck his senses in a peculiar manner, to