Aristotle’s Physics Reviewed. 
171 
is nature? A collective name for those things, together with their causes, 
etc., which have in themselves a principle of motion or change (kinesis). 
(II. 1.) It is necessary, then, to have clear concepts of matter, form, 
cause, change, including local motion, time and place or space, with their 
correlated ideas, and this is the aim of the treatise now before us. 
(I. 6, 7). Two principles at least, perhaps three, are necessary to ex¬ 
plain nature as it is known by us, viz., a passive matter, and an active 
force, manifested in contrary phenomena; (attraction and repulsion, heat 
and cold, etc.) 
Motion, kinesis, taken in the widest sense, is the (continuous) transition 
from a potential state to an actual state. It is either a change of quantity, 
or of quality, or of place. But the three are reducible to one, viz., local 
motion. (VIII, 1.) If to these we add the change from potential to actual 
being in generation, and its contrary, decay (phthora) we shall have the 
whole sphere of changes perceived in nature. 
II. 2. Applied mathematics consider the purely intelligible and un¬ 
changeable element which is found in nature, underlying all its changes. 
II. 3. We account for any of those changes which we perceive in na¬ 
ture, when we assign their causes. But the word cause is very ambiguous, 
and needs definition. All uses of the word are reducible to four: (1). The 
material of the thing which comes into being may be called its cause, (con¬ 
dition), as marble of the statue; (2). The form or pattern, as the idea of 
an oak is that towards which the acorn develops; (3). The efficient cause 
or originator of the change which may itself be a changeable antecedent; 
(4). The end, or final cause, or reason why. Why does one take exercise? 
The cause is not fully given, if we name the man, describe the exercise 
and account for muscular contraction; we add (II, 3), another cause; sc., the 
exercise is for the sake of health. 
In discussing cause, also, we must not overlook the fact (II, 7) that two 
very different principles are requisite in explaining nature, sc., the sensible 
antecedents, and the intelligible principle which is not physical nor subject 
to change. Nature requires for its explication the supernatural. 
II. 8. The discussion of final causes is of such interest in connection 
with modern physics, and especially with reference to recent questions in 
Natural history, that I may perhaps be allowed to present it in condensed 
paraphrase. Why would it not be sufficient explanation of the expansion 
of water cooled down to 40 degrees of Fahrenheit, if we could, as we can¬ 
not, assign its physical antecedents ? But our mind recognizes a relation 
to the good of the world, an order and connection of things. And we must 
assign chance, spontaneous action, or design, in accounting for that order,, 
if we assign any cause for it. (Chance, here, does not mean the entire ab¬ 
sence of law, but a law which does not enter into the series of events in 
question.) 
By chance results may be obtained, indeed, as, when our guest came for 
other reasons but took a bath at our house, we say that by chance he took a 
