ng to the
class of association; and are termed ideas of suggestion.

II. Lastly, the method already explained of classing ideas into those
excited by irritation, sensation, volition, or association, we hope will be
found more convenient both for explaining the operations of the mind, and
for comparing them with those of the body; and for the illustration and the
cure of the diseases of both, and which we shall here recapitulate.

1. Irritative ideas are those, which are preceded by irritation, which is
excited by objects external to the organs of sense: as the idea of that
tree, which either I attend to, or which I shun in walking near it without
attention. In the former case it is termed perception, in the latter it is
termed simply an irritative idea.

2. Sensitive ideas are those, which are preceded by the sensation of
pleasure or pain; as the ideas, which constitute our dreams or reveries,
this is called imagination.

3. Voluntary ideas are those, which are preceded by voluntary exertion, as
when I repeat the alphabet backwards: this is called recollection.

4. Associate ideas are those, which are preceded by other ideas or muscular
motions, as when we think over or repeat the alphabet by rote in its usual
order; or sing a tune we are accustomed to; this is called suggestion.

III. 1. Perceptions signify those ideas, which are preceded by irritation
and succeeded by the sensation of pleasure or pain, for whatever excites
our attention interests us; that is, it is accompanied with, pleasure or
pain; however slight may be the degree or quantity of either of them.

The word memory includes two classes of ideas, either those which, are
preceded by voluntary exertion, or those which are suggested by their
associations with other ideas.

2. Reasoning is that operation of the sensorium, by which we excite two or
many tribes of ideas; and then re-excite the ideas, in which they differ,
or correspond. If we determine this difference, it is called judgment; if
we in vain endeavour to determine it, it is called doubting.

If we re-excited the ideas, in which they differ, it is called
distinguishing. If we re-excite those in which they correspond, it is
called comparing.

3. Invention is an operation of the sensorium, by which we voluntarily
continue to excite one train of ideas, suppose the design of raising water
by a machine; and at the same time attend to all other ideas, which are
connected with this by every kin