is good; for good
health is by far the most important element in human happiness. It
follows from all this that the greatest of follies is to sacrifice
health for any other kind of happiness, whatever it may be, for gain,
advancement, learning or fame, let alone, then, for fleeting sensual
pleasures. Everything else should rather be postponed to it.

But however much health may contribute to that flow of good spirits
which is so essential to our happiness, good spirits do not entirely
depend upon health; for a man may be perfectly sound in his physique
and still possess a melancholy temperament and be generally given up
to sad thoughts. The ultimate cause of this is undoubtedly to be
found in innate, and therefore unalterable, physical constitution,
especially in the more or less normal relation of a man's
sensitiveness to his muscular and vital energy. Abnormal sensitiveness
produces inequality of spirits, a predominating melancholy, with
periodical fits of unrestrained liveliness. A genius is one whose
nervous power or sensitiveness is largely in excess; as Aristotle[1]
has very correctly observed, _Men distinguished in philosophy,
politics, poetry or art appear to be all of a melancholy temperament_.
This is doubtless the passage which Cicero has in his mind when
he says, as he often does, _Aristoteles ait omnes ingeniosos
melancholicos esse_.[2] Shakespeare has very neatly expressed this
radical and innate diversity of temperament in those lines in _The
Merchant of Venice_:

[Footnote 1: Probl. xxx., ep. 1]

[Footnote 2: Tusc. i., 33.]

_Nature has framed strange fellows in her time;
Some that will evermore peep through their eyes,
And laugh, like parrots at a bag-piper;
And others of such vinegar aspect,
That they'll not show their teeth in way of smile,
Though Nestor swear the jest be laughable_.

This is the difference which Plato draws between [Greek: eukolos]
and [Greek: dyskolos]--the man of _easy_, and the man of _difficult_
disposition--in proof of which he refers to the varying degrees of
susceptibility which different people show to pleasurable and painful
impressions; so that one man will laugh at what makes another despair.
As a rule, the stronger the susceptibility to unpleasant impressions,
the weaker is the susceptibility to pleasant ones, and _vice versa_.
If it is equally possible for an event to turn out well or ill,
the [Greek: dyskolos] will be annoyed or grieved if the issue