I return then to the consideration of the alleged shortness of life. I
mentioned in the beginning of this Essay, that "human life consists of
years, months and days; each day containing twenty-four hours." But,
when I said this, I by no means carried on the division so far as it
might be carried. It has been calculated that the human mind is capable
of being impressed with three hundred and twenty sensations in a second
of time.(11)

(11) See Watson on Time, Chapter II.

"How infinitely rapid is the succession of thought! While I am speaking,
perhaps no two ideas are in my mind at the same time, and yet with
what facility do I slide from one to another! If my discourse be
argumentative, how often do I pass in review the topics of which it
consists, before I utter them; and, even while I am speaking, continue
the review at intervals, without producing any pause in my discourse!
How many other sensations are experienced by me during this period,
without so much as interrupting, that is, without materially diverting,
the train of my ideas! My eye successively remarks a thousand objects
that present themselves. My mind wanders to the different parts of my
body, and receives a sensation from the chair on which I sit, or the
table on which I lean. It reverts to a variety of things that occurred
in the course of the morning, in the course of yesterday, the most
remote from, the most unconnected with, the subject that might seem
wholly to engross me. I see the window, the opening of a door, the
snuffing of a candle. When these most perceptibly occur, my mind passes
from one to the other, without feeling the minutest obstacle, or being
in any degree distracted by their multiplicity(12)."

(12) Political Justice, Book IV, Chapter ix.

If this statement should appear to some persons too subtle, it may
however prepare us to form a due estimate of the following remarks.

"Art is long." No, certainly, no art is long, compared with the natural
duration of human life from puberty to old age. There is perhaps no art
that may not with reasonable diligence be acquired in three years, that
is, as to its essential members and its skilful exercise. We may improve
afterwards, but it will be only in minute particulars, and only by fits.
Our subsequent advancement less depends upon the continuance of our
application, than upon the improvement of the mind generally, the
refining of our taste, the strengthening our judgment,