The Stoics thought little of that device to save free will: 'they do not allow Epicurus to swerve his atoms a
jot, for he thereby introduces an uncaused motion', Chrysippus insisted that, 'since universal nature
extends to everything, it will be necessary for everything whatever to occur in accordance with nature and
with its rational principle, in due order and ineluctably'. Fate is the name the Stoics gave to the chain of
causes and effects which binds the universe together: 'everything happens in accordance with fate'.
The Sceptical Academy launched a major attack against this Stoic position. One of their arguments - the
'Lazy Argument', probably formulated by Arcesilaus - ran as follows: 'If it is fated for you to recover from
this illness, you will recover whether you call a doctor or not; again, if it is fated for you not to recover
from this illness, you will not recover whether you call a doctor or not; but one or the other is fated:
therefore it is pointless to call a doctor.' Carneades produced a different line of thought: 'If everything
comes about by antecedent causes, everything comes about in a web or net of natural interconnections; if
that is so, necessity causes everything; if that is true, nothing is in our power.'
The debate between the Academy and the Stoa was long and intricate. Chrysippus had a subtle reply to
the Lazy Argument, but his most interesting manoeuvre depended on a distinction among types of cause.
'Some causes are perfect and principal, others auxiliary and proximate. Thus when we say that everything
happens by fate in virtue of antecedent causes, we wish to be understood to mean not perfect and principal
but auxiliary and proximate causes.' An example makes the point clear. A man places a cylinder on a flat
surface and gives it a push: it rolls. 'Just as the man who pushed the cylinder gave a start to its motion but
did not make it such as to roll, so an object that appears to us will impress us and as it were seal its form
in our mind, but assent will be in our power; and, as we said in the case of the cylinder, assent, though
pushed externally, will for the rest move by its own force and nature'. The antecedent cause - the man's
push - makes the cylinder move; but it does not determine the cylinder to roll rather than to slide. That the
cylinder rolls is due to its own nature, not to external circumstances. Similarly, Chrysippus urges, the
antecedent cause - the impression of an external object - causes the mind to move; but it does not
determine the direction of the movement. That the mind assents to or dissents from the impression is due
to its own nature - it is something within our power.
That ingenious comparison did not end the debate. Chrysippus' successors elaborated his classification of
causes, and the attempt to reconcile freedom and fatalism exercised the Stoa for the whole of its history.
Whether or not the attempt succeeded, it inspired the subtlest analysis of the notion of causation in the
history of philosophy.
Logic
Physics will succour ethics only if it is grounded in firm knowledge. Here the logical part of philosophy
enters; for, according to the Stoics, 'everything is discerned by way of logical study - both what falls
within the province of physics and what falls within the province of ethics'. Now things are either 'evident'
or 'unclear'. If evident, they are grasped 'immediately' or 'directly'; if unclear, they are grasped indirectly
and by the mediation of other things. Thus logic will have two main aspects: it will provide a 'criterion of
truth', as the Hellenistic philosophers called it, by which we may judge what is evident; and it will offer a