But to enter into details here would be out of place. According to this Rational Psychology, the soul was originally and in its essence a =perceiving= substance, and only as a consequence thereof did it become possessed of volition. According as it carried on these two modes of its activity, Perception and Volition, conjoined with the body, or incorporeal, and entirely _per se_, so it was endowed with a lower or higher faculty of perception, and of volition in like kind. In its higher faculty the immaterial soul was active solely by itself, and without co-operation of the body. In this case it was _intellectus purus_, being composed of concepts, belonging exclusively to itself, and of the corresponding acts of will, both of which were absolutely spiritual, and had nothing sensuous about them--the sensuous being derived from the body.[20] So that it perceived nothing else but pure Abstracts, Universals, innate conceptions, _aeternae veritates_, etc.; wherefore also its volition was entirely controlled by purely spiritual ideas like these. On the other hand, the soul's =lower= faculty of Perception and Volition was the result of its working in concert and close union with the various organs of the body, whereby a prejudicial effect was produced on its an mixed spiritual activity. Here, _i.e._, to this =lower= faculty, was supposed to belong every =intuitive= perception, which consequently would have to be obscure and confused, while the =abstract=, formed by separating from objects their qualities, would be clear! The will, which was determined by preceptions thus sensuously conditioned, formed the lower Volition, and it was for the most part bad; for its acts were guided by the impulse of the senses; while the other will (the higher) was untrammelled, was guided by Pure Reason, and appertained only to the immaterial soul. This doctrine of the Cartesians has been best expounded by De la Forge, in his _Tractatus de Mente Humana_, where in chap. 23 we read:[21] _Non nisi eadem voluntas est, quae appellatur appetitus sensitivus, quando excitatur per judicia, quae formantur consequenter ad perceptiones sensuum; et quae appetitus rationalis nominatur, cum mens judicia format de propriis suis ideis, independenter a cogitationibus sensuum confusis, quae inclinationum ejus sunt causae.... Id, quod occasionem dedit, ut duae istae diversae voluntatis propensiones pro duobus diversis appetitibus sumerentur, est, quod saepissime unus alteri opponatur, quia propositum, quod mens superaedificat propriis suis perceptionibus, non semper consentit cum cogitationibus, quae menti a corporis dispositione suggeruntur, per quam saepe obligatur ad aliquid volendum, dum ratio ejus earn aliud optare facit._