Routledge History of Philosophy Volume IV

238 RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM
or effects from causes. Method prescribes, as a stage in the search for causes, the
identification of universal things in particulars, that is, the most general properties
that can be inferred from the analysis of descriptions of specific phenomena. But
to find the relevant universals is not yet to know the ultimate cause of the
phenomena, for the universals themselves have a universal cause, which is
motion.
Finding causes is a matter of finding one of the many varieties of motion that
is capable of generating a given effect. The varieties of motion that each of the main
branches of science are concerned with are described in article 6 of Chapter 6 of
De Corpore. Geometry studies motion in general—motion in the abstract—in
body in general (E I 71). The rest of the sciences deal with differentiated motions
in differentiated bodies. Thus pure mechanics deals with motions in bodies
considered only as numerically distinct, and as having parts. It deals with the
effects of motions of the parts of bodies on whole bodies, and also with the
transmission of motion in collisions involving different numbers of bodies (E I
71–2). Physics deals with the sensory effects in animate bodies of motions
transmitted by inanimate bodies. It deals also with the after-effects of sensory
episodes and images compounded in imagination (E I 71; ch. 25, vii, E I 396–7;
cf. L, ch. 1, E III 6). Moral philosophy, or, perhaps more accurately, moral
psychology, deals with further after-effects of sensation in the form of passions.
In this branch of science ‘we are to consider the emotions of the mind, namely,
appetite, aversion, love, benevolence, hope, fear, anger, emulation, envy etc.’
(De corp. ch. 1, vi, E I 72).
It should now be clear that for Hobbes physics and moral psychology are
sciences of motion, and therefore branches of mechanics. Both sciences are
supposed to be concerned with the motions of the mind, physics because it
considers the nature of sensation, and moral psychology because it studies some
of the psychological effects of sensation. It is clear also that the psychological
parts of physics and moral psychology are at the same time, but secondarily,
sciences of matter, and support the classification of Hobbes as a materialist.
It is time to look at these sciences in more detail. The theory of sensation is
not only a part of Hobbes’s physics, but the part that Hobbes thinks has to be
expounded first. The reason is that the data explained by physics are appearances,
and these appearances could not exist if there were no sensation to produce
them. Sense being what provides the data of physics, how does it work?
Hobbes’s answer is that it works by reaction, reaction to motion propagated
through the parts of the sense organs. The process that culminates in sense
experience affects the whole living creature, but it starts with pressure on some
external and sensitive part of the living creature. This is the ‘uttermost’ part of
the sense organ. When
it is pressed, it no sooner yields, but the part next within it is pressed also;
and, in this manner, the pressure or motion is propagated through all the parts
of the sense organ to the innermost.