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is the efficient cause of savour。
（a） Of these three hypotheses； the falsity of that held by
Empedocles is only too evident。 For we see that when pericarpal fruits
are plucked ＇from the tree＇ and exposed in the sun； or subjected to
the action of fire； their sapid juices are changed by the heat；
which shows that their qualities are not due to their drawing anything
from the water in the ground； but to a change which they undergo
within the pericarp itself； and we see； moreover； that these juices；
when extracted and allowed to lie； instead of sweet become by lapse of
time harsh or bitter； or acquire savours of any and every sort； and
that； again； by the process of boiling or fermentation they are made
to assume almost all kinds of new savours。
（b） It is likewise impossible that water should be a material
qualified to generate all kinds of Savour germs ＇so that different
savours should arise out of different parts of the water＇； for we
see different kinds of taste generated from the same water； having
it as their nutriment。
（C） It remains； therefore； to suppose that the water is changed by
passively receiving some affection from an external agent。 Now； it
is manifest that water does not contract the quality of sapidity
from the agency of Heat alone。 For water is of all liquids the
thinnest； thinner even than oil itself； though oil； owing to its
viscosity； is more ductile than water； the latter being uncohesive
in its particles； whence water is more difficult than oil to hold in
the hand without spilling。 But since perfectly pure water does not；
when subjected to the action of Heat； show any tendency to acquire
consistency； we must infer that some other agency than heat is the
cause of sapidity。 For all savours ＇i。e。 sapid liquors＇ exhibit a
comparative consistency。 Heat is； however； a coagent in the matter。
Now the sapid juices found in pericarpal fruits evidently exist also
in the earth。 Hence many of the old natural philosophers assert that
water has qualities like those of the earth through which it flows；
a fact especially manifest in the case of saline springs； for salt
is a form of earth。 Hence also when liquids are filtered through
ashes； a bitter substance； the taste they yield is bitter。 There are
many wells； too； of which some are bitter； others acid； while others
exhibit other tastes of all kinds。
As was to be anticipated； therefore； it is in the vegetable
kingdom that tastes occur in richest variety。 For； like all things
else； the Moist； by nature's law； is affected only by its contrary；
and this contrary is the Dry。 Thus we see why the Moist is affected by
Fire； which as a natural substance； is dry。 Heat is； however； the
essential property of Fire； as Dryness is of Earth； according to
what has been said in our treatise on the elements。 Fire and Earth；
therefore； taken absolutely as such； have no natural power to
affect； or be affected by； one another； nor have any other pair of
substances。 Any two things can affect； or be affected by； one
another only so far as contrariety to the other resides in either of
them。
As； therefore； persons washing Colours or Savours in a liquid
cause the water in which they wash to acquire such a quality ＇as
that of the colour or savour＇； so nature； too； by washing the Dry
and Earthy in the Moist； and by filtering the latter； that is；
moving it on by the agency of heat through the dry and earthy； imparts
to it a certain quality。 This affection； wrought by the aforesaid
Dry in the Moist； capable of transforming the sense of Taste from
potentiality to actuality； is Savour。 Savour brings into actual
exercise the perceptive faculty which pre…existed only in potency。 The
activity of sense…perception in general is analogous； not to the
process of acquiring knowledge； but to that of exercising knowledge
already acquired。
That Savours； either as a quality or as the privation of a
quality； belong not to every form of the Dry but to the Nutrient； we
shall see by considering that neither the Dry without the Moist； nor
the Moist without the Dry； is nutrient。 For no single element； but
only composite substance； constitutes nutriment for animals。 Now；
among the perceptible elements of the food which animals assimilate；
the tangible are the efficient causes of growth and decay； it is qua
hot or cold that the food assimilated causes these； for the heat or
cold is the direct cause of growth or decay。 It is qua gustable；
however； that the assimilated food supplies nutrition。 For all
organisms are nourished by the Sweet ＇i。e。 the 'gustable' proper＇；
either by itself or in combination with other savours。 Of this we must
speak with more precise detail in our work on Generation： for the
present we need touch upon it only so far as our subject here
requires。 Heat causes growth； and fits the food…stuff for
alimentation； it attracts ＇into the organic system＇ that which is
light ＇viz。 the sweet＇； while the salt and bitter it rejects because
of their heaviness。 In fact； whatever effects external heat produces
in external bodies； the same are produced by their internal heat in
animal and vegetable organisms。 Hence it is ＇i。e。 by the agency of
heat as described＇ that nourishment is effected by the sweet。 The
other savours are introduced into and blended in food ＇naturally＇ on a
principle analogous to that on which the saline or the acid is used
artificially； i。e。 for seasoning。 These latter are used because they
counteract the tendency of the sweet to be too nutrient； and to
float on the stomach。
As the intermediate colours arise from the mixture of white and
black； so the intermediate savours arise from the Sweet and Bitter；
and these savours； too； severally involve either a definite ratio；
or else an indefinite relation of degree； between their components；
either having certain integral numbers at the basis of their
mixture； and； consequently； of their stimulative effect； or else being
mixed in proportions not arithmetically expressible。 The tastes
which give pleasure in their combination are those which have their
components joined in a definite ratio。
The sweet taste alone is Rich； ＇therefore the latter may be regarded
as a variety of the former＇； while ＇so far as both imply privation
of the Sweet＇ the Saline is fairly identical with the Bitter。
Between the extremes of sweet and bitter come the Harsh； the
Pungent； the Astringent； and the Acid。 Savours and Colours； it will be
observed； contain respectively about the same number of species。 For
there are seven species of each； if； as is reasonable； we regard Dun
＇or Grey＇ as a variety of Black （for the alternative is that Yellow
should be classed with White； as Rich with Sweet）； while ＇the
irreducible colours； viz。＇ Crimson； Violet；