Whatsoever we endeavour in obedience to reason is nothing further than to understand; neither does the mind, in so far as it makes use of reason, judge anything to be useful to it, save such things as are conducive to understanding.
Proof .-- The effort for self--preservation is nothing else but the essence of the thing in question (III.

vii.), which, in so far as it exists such as it is, is conceived to have force for continuing in existence (III.

vi.) and doing such things as necessarily follow from its given nature (see the Def.

of Appetite, III.ix.

note).