[846] Prop. viii.
[847] Schol., prop. xl.
85. Thus we form universal ideas; first, by singulars, represented by the senses confusedly, imperfectly and disorderly; secondly, by signs, that is, by associating the remembrance of things with words; both of which he calls imagination, or primi generis cognitio; thirdly, by what he calls reason, or secundi generis cognitio; and fourthly, by intuitive knowledge, or tertii generis cognitio.[848] Knowledge of the first kind is the only source of error; the second and third being necessarily true.[849] These alone enable us to distinguish truth from falsehood. Reason contemplates things not as contingent but necessary; and whoever has a true idea, knows certainly that his idea is true. Every idea of a singular existing thing involves the eternal and infinite being of God. For nothing can be conceived without God, and the ideas of all things, having God for their cause, considered under the attribute of which they are modes, must involve the conception of the attribute, that is, the being of God.[850]
[848] Schol. ii., prop. xl.
[849] Prop. xli., xlii, et sequent.
[850] Prop. xlv.
86. It is highly necessary to distinguish images, ideas, and words, which many confound. Those who think ideas consists in images which they perceive, fancy that ideas of which we can form no image are but arbitrary figments. They look at ideas, as pictures on a tablet, and hence do not understand that an idea, as such, involves an affirmation or negation. And those who confound words with ideas, fancy they can will something contrary to what they perceive, because they can affirm or deny it in words. But these prejudices will be laid aside by him who reflects that thought does not involve the conception of extension; and therefore that an idea, being a mode of thought, neither consists in images nor in words, the essence of which consists in corporeal motions, not involving the conception of thought.[851]
[851] Schol., prop. xlix.
87. The human mind has an adequate knowledge of the eternal and infinite being of God. But men cannot imagine God as they can bodies, and hence have not that clear perception of his being which they have of that of bodies, and have also perplexed themselves by associating the word God with sensible images, which it is hard to avoid. This is the chief source of all error, that men do not apply names to things rightly. For they do not err in their own minds, but in this application; as men who cast up wrong see different numbers in their mind from those in the true result.[852]
[852] Prop. xlvii. Atque hinc pleræque oriuntur controversiæ, nempe, quia homines mentem suam non recte explicant, vel quia alterius mentem male interpretantur.