or of figure: an excess of heat produces smarting, of cold another kind of
pain; it is probable by this sense of heat the pain produced by caustic
bodies is perceived, and of electricity, as all these are fluids, that
permeate, distend, or decompose the parts that feel them.

* * * * *

SECT. XV.

OF THE CLASSES OF IDEAS.

I. 1. _Ideas received in tribes._ 2. _We combine them further, or
abstract from these tribes._ 3. _Complex ideas._ 4. _Compounded ideas._
5. _Simple ideas, modes, substances, relations, general ideas._ 6.
_Ideas of reflexion._ 7. _Memory and imagination imperfectly defined.
Ideal presence. Memorandum-rings._ II. 1. _Irritative ideas.
Perception._ 2. _Sensitive ideas, imagination._ 3. _Voluntary ideas,
recollection._ 4. _Associated ideas, suggestion._ III. 1. _Definitions
of perception, memory._ 2. _Reasoning, judgment, doubting,
distinguishing, comparing._ 3. _Invention._ 4. _Consciousness._ 5.
_Identity._ 6. _Lapse of time._ 7. _Free-will._

I. 1. As the constituent elements of the material world are only
perceptible to our organs of sense in a state of combination; it follows,
that the ideas or sensual motions excited by them, are never received
singly, but ever with a greater or less degree of combination. So the
colours of bodies or their hardnesses occur with their figures: every smell
and taste has its degree of pungency as well as its peculiar flavour: and
each note in music is combined with the tone of some instrument. It appears
from hence, that we can be sensible of a number of ideas at the same time,