PHILOSOPHY, MENTAL. 
b, c, d, &c. B will raise c, d, &c. : and 
though the ideas do not rise precisely in the 
same instant, yet they come nearer and 
nearer together than the sensations did in 
their original impression ; so that these 
ideas are at last associated synchronously 
as they were from the first successively. 
56. Case 4. All compound impressions, 
A-f-B-l-C + D, &c. or ABCD, &o. 
(according as they are received by different 
organs, or the same) after sufficient repeti- 
tion leave behind their compound ideas 
d, &c. or abed, &c. w'hich recur 
every now and then by means of sensations, 
or ideas, with which the whole compound, or 
any one or more of the parts A, B, C, D, 
&c. have been associated. Now in these 
recurrences of compound ideas, the parts 
are further associated, and more intimately 
united to one another, agreeably to what was 
observed above, so as to form a compound 
or complex idea which shall appear to the 
mind as one single idea.— As the same 
causes produce the recurrence of the 
compounded idea's, in whatsoever way the 
union was first produced, the same remark 
may be made under each of the cases as 
have been under this and the first case, 
respecting the causes and effects of such 
recurrence. 
57. On the whole it may appear to the 
reader, that the simple ideas of sensation 
must run into clusters and combinations, 
by association ; and that each of these will, 
at last, coalesce into one compound or 
complex idea. It appears also from obser- 
vation, that many of our mental or intel- 
lectual ideas (that is those in which no par- 
ticular idea ot sensation is perceptible) 
such as those which belong to the heads of 
beauty, honour, moral qualities, &c. are, in 
fact, thus composed of parts which by de- 
grees coalesce into one complex idea. And 
as this coalescence of simple into complex 
ideas is thus evinced, both by the theory of 
association and by observation, so it may 
be illustrated and further confirmed, by the 
similar coalescence of letters into syllables 
and words, in which association is likewise 
a chief instrument. 
58. If the number of simple ideas which 
compose the complex idea be very great, it 
may happen that the complex ideas shall 
not appear to bear any relation to its com- 
ponent parts, nor to the external senses by 
which the origiiral sensations were received. 
The reason of this is, that each single idea 
is overpowered by the sum of all the rest, as 
VOL. V, 
soon as they are all intimately united toge- 
ther. Thus in very compound medicines, 
the several tastes and flavours of the sepa- 
rate ingredients are lost and overpowered 
by the complex one of the whole mass : so 
that this has a taste and flavour of its own, 
which appears to be simple and original. 
Thus also w'liite appears, and is vulgarly 
thought to be, the simplest of all colours, 
while yet it really arises from a certain 
mixture of the seven primary colours in their 
due shades and proportions. And to re- 
sume the illustration above mentioned, to 
one unacquainted with the arts of reading 
and writing, it could not appear probable, 
that the great variety of complex sounds in 
language are to be analysed into a few sim- 
ple sounds. One may hope, therefore, that 
by pursuing and perfecting the doctrine of 
association, we may some time or other be 
enabled to analyse all that vast variety of 
complex ideas which pass under the names 
of ideas of reflection, abstract ideas, de- 
sires, affections, &c. into their simple com- 
ponentparts, that is, into the simple ideas of 
sensation of which they are formed. This 
would be greatly analogous to the represen- 
tation of complex articulate sounds by al- 
phabetical signs, and to the revolution of 
colours, or of natural bodies, into their sim- 
ple constituent parts. The complex ideas 
here spoken of are generally excited by 
words or visible objects; but they are also 
connected with other external impressions, 
and depend upon them as symbols. In 
whatever way we consider them, the trains 
of them which are presented to the mind 
seem to depend upon the then present state 
of the body, the external impressions and 
the remaining influence of prior impressions 
and associations taken together. 
59. As simple ideas of sensation run into 
complex ones by association, so complex 
ideas run into decomplex ones by asso- 
ciation. But here the varieties of the asso- 
ciations, which increase with the com- 
plexity, hinder particular ones fiom being 
so close and permanent between the com- 
plex parts of decomplex ideas, as between 
the simple parts of complex ones. 
60. The simple ideas of sensation are not 
alt equally and uniformly concerned in 
forming complex and decomplex ideas, but 
on the contrary some occur much oftener 
than others ; and the same holds good of 
complex ideas as the component parts of 
decomplex ideas : and innumerable combi- 
nations never occur at all in real life, and 
