By 'quality' I mean that in virtue of which people are said to be
such and such.
Quality is a term that is used in many senses. One sort of
quality let us call 'habit' or 'disposition'. Habit differs from
disposition in being more lasting and more firmly established.
The various kinds of knowledge and of virtue are habits, for
knowledge, even when acquired only in a moderate degree, is, it
is agreed, abiding in its character and difficult to displace,
unless some great mental upheaval takes place, through disease or
any such cause. The virtues, also, such as justice,
self-restraint, and so on, are not easily dislodged or dismissed,
so as to give place to vice.
By a disposition, on the other hand, we mean a condition that is
easily changed and quickly gives place to its opposite. Thus,
heat, cold, disease, health, and so on are dispositions. For a
man is disposed in one way or another with reference to these,
but quickly changes, becoming cold instead of warm, ill instead
of well. So it is with all other dispositions also, unless
through lapse of time a disposition has itself become inveterate
and almost impossible to dislodge: in which case we should
perhaps go so far as to call it a habit.
It is evident that men incline to call those conditions habits
which are of a more or less permanent type and difficult to
displace; for those who are not retentive of knowledge, but
volatile, are not said to have such and such a 'habit' as regards
knowledge, yet they are disposed, we may say, either better or
worse, towards knowledge. Thus habit differs from disposition in
this, that while the latter in ephemeral, the former is permanent
and difficult to alter.
Habits are at the same time dispositions, but dispositions are
not necessarily habits. For those who have some specific habit
may be said also, in virtue of that habit, to be thus or thus
disposed; but those who are disposed in some specific way have
not in all cases the corresponding habit.