Spinoza's Ethics: III.P3

Mentis actiones ex solis ideis adæquatis oriuntur, passiones autem a solis inadæquatis pendent.

The actions of the mind arise from only adequate ideas, meanwhile the passions weigh from only inadequate ones.

DEMONSTRATIO: Primum quod mentis essentiam constituit, nihil aliud est quam idea corporis actu existentis (per propositiones 11 et 13 partis II) quæ (per propositionem 15 partis II) ex multis aliis componitur quarum quædam (per corollarium propositionis 38 partis II) sunt adæquatæ, quædam autem inadæquatæ (per corollarium propositionis 29 partis II). Quicquid ergo ex mentis natura sequitur et cujus mens causa est proxima per quam id debet intelligi, necessario ex idea adæquata vel inadæquata sequi debet. At quatenus mens (per propositionem 1 hujus) ideas habet inadæquatas eatenus necessario patitur; ergo mentis actiones ex solis ideis adæquatis sequuntur et mens propterea tantum patitur quia ideas habet inadæquatas. Q.E.D.

First what establishes the essence of the mind, nothing other than which the idea of the existence of the actual body (by IIP11 and IIP13) which (by IIP15) is made up of many others of which certain (by IIP38C) are adequate, moreover certain are inadequate (by IIP29C). Thus whatever follows from the nature of the mind and of which the mind is the exact cause by which it ought to be understood, ought to follow necessarily from an idea either adequate or inadequate. But insofar as the mind (by IIIP1) has inadequate ideas it necessarily suffers thus far; therefore the actions of the mind follow from the adequate ideas alone and meanwhile the mind suffers so much because it has inadequate ideas.

SCHOLIUM: Videmus itaque passiones ad mentem non referri nisi quatenus aliquid habet quod negationem involvit sive quatenus consideratur ut naturæ pars quæ per se absque aliis non potest clare et distincte percipi et hac ratione ostendere possem passiones eodem modo ad res singulares ac ad mentem referri nec alia ratione posse percipi sed meum institutum est de sola mente humana agere.

Thus we see passions do not refer to the mind unless insofar as something which involves negation or insofar as it is considered that a part of nature which is not able to be perceived clearly and distinctly through itself and from others and by this way I am able to show that the passions in this way refer to singular things as to the mind and not by some other way are able to be perceived but is my principle to discuss concerning the human mind.  

Here Spinoza attempts a first discussion of the passions. His use of the verb pendere in contrast to oriri is interesting as an illustration of the power of actions versus the weight of passions. The scholium discusses that passions are either (from a thinking attribute) a negation or (from an extending attribute) a dysfunction of the body in its incapacity. This sets up that passions are truly extending things in Spinoza's parallelism. Thus, imaginations of the mind do have place in the attribute of extending. But Spinoza clarifies that he is only going to address those of the human mind or the attribute of thinking. This is important because it often seems that Spinoza's focus on imagination creates a non-match in his parallelism.