Chrysippus, Fragments from the Passions 3

There do exist parts of the soul out of which the reason in it and the disposition in the reason are composed. 

And the soul is honorable or shameful in accordance with the condition of its leading part with respect to its proper divisions. 

Chrysippus, Fragments from the Passions 2

That is why it is not off the mark to say, as some people do, that a passion of the soul is an unnatural motion, as is the case with fear and desire and things like that; for all such motions and conditions are disobedient to reason and reject it. 

And so we say that such people are irrationally moved, not as though they make a bad calculation, which would be the sense opposite to "reasonably", but rather in the sense of a rejection of reason. . . . 

That is what such conditions are like, uncontrolled, as though they were not masters of themselves but were carried away in the way that those who run strenuously are swept away and cannot control their motion. 

But those who move according to reason, as though it were their leader, and steer their course by it wherever it might lead, these people are in control of this sort of motion and the impulses that go with it. 

Chrysippus, Fragments from The Passions 1

These fragments from On the Passions by Chrysippus are to be found in Galen's On the Doctrines of Hippocrates and Plato. 

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We must first keep in mind that the rational animal is by nature such as to follow reason and to act according to reason as a guide. 

Nevertheless, he often moves toward some things and away from some things in another way, disobediently to reason, when he is pushed too far, or to excess. Both definitions of passion, the natural motion which arises irrationally in this way and the excessiveness in the impulses, are in terms of this motion. 

For this irrationality must be taken to be disobedient to reason and turning its back on reason. 

And it is in terms of this motion that we also say in ordinary usage that some people are "pushed" and "moved irrationally without reason and judgment".

For we do not use these expressions as if someone is moved mistakenly, and because he overlooks something that is according to reason, but most especially according to the motion Zeno outlines, since the rational animal does not naturally move in accordance with his soul in this way, but rather in accordance with reason. . . . 

The excess of the impulse was also spoken of in terms of this, because they overstep the symmetry of impulses which is proper to themselves and natural. What I say would be made easier to understand by means of these examples. 

In walking according to impulse, the motion of the legs is not excessive but is in a sense coextensive with the impulse, so that it can come to a standstill when the walker wishes, or change direction. 

But in the case of those who are running according to impulse, this sort of thing is no longer the case, but the motion of the legs exceeds the impulse so that it is carried away, and does not change direction obediently in this way as soon as they start to do so. 

I think something similar to these motions of the legs occurs in the impulses, because of the overstepping of the symmetry which is according to reason, so that whenever one has an impulse he is not obedient with respect to it—the excess being beyond the impulse in the case of running and beyond reason in the case of impulse. 

For the symmetry of natural impulse is that according to reason and is as far as reason thinks proper. Therefore, since the overstepping is according to this standard and in this way, the impulse is said to be excessive and an unnatural and irrational motion of the soul.