Nogmaals 2/8, 2/8c en 2/8s over het kennen van niet bestaande dingen
Of: Wat als je "formele essenties" als "mogelijkheden" leest – zoals Alan Donagan deed 
In het laatste hoofdstuk, “Last Things”, van zijn boek Spinoza (1988) behandelt hij de ‘pijlers’ waarop Spinoza zijn theorie baseert over wat er van de geest overblijft zonder relatie met het lichaam. Die bouwstenen behandelt hij in achtereenvolgende paragrafen. De eerste is: “The Identity of Individual Human Minds.” De volgende, en die neem ik hier in zijn geheel over, is:
10.3. God's Cognition of Non-Existent Individuals
The first of the pillars supporting Spinoza's conclusions about the human mind's existence without relation to the body is now in place. What of the second: his theory of God's cognition of non-existent individuals or 'singulars'? Some critics, arguing that his principle of mode identity, that 'the order and connection of ideas is the same as the order and connection of things' (E2p7), implies that the expressions of a mode under each of the attributes, extension and thought, must be strictly symmetrical, contend that he has denied himself the right to have such a theory. [verwijst naar Bennett]. According to that principle, they maintain, there cannot be existent ideas without existent bodies as counterparts. Since the counterparts of non-existent possible bodies are non-existent possible ideas, there cannot be in God existent ideas corresponding to non-existent things. Hence God cannot cognize non-existent bodies.
Immediately after stating his principle of mode identity, however, Spinoza excluded this interpretation of it by asserting that 'The ideas of singular things, or of modes, that do not exist, must be comprehended in God's infinite idea in the same way as the formal essences of the singular things, or modes, are contained in God's attributes' (E2p8 my emphasis). To elucidate, I cannot do better than translate Matheron's comment:
God, inasmuch as he conceives himself, necessarily conceives all the consequences of his nature (E2p3); he conceives, in other words, all the essences of all the finite modes, and, by virtue of that totalization, the order in which they pass one after another into existence: so many essences of singular things, so many ideas which express them objectively in the infinite Understanding. Now these ideas are eternal without qualification: their claim to exist encounters no obstacle; for nothing prevents the infinite Understanding from thinking simultaneously the successive modes of Extension; simply from the fact that they are deduced from the nature of God, they exist, independently of all temporal conditions. The ideas of non-existent bodies therefore have a slightly different status from that of their ideata; the former exist only so far as they are comprehended in the attribute Extension (E2p8c), as being logical possibilities, conceivable combinations of motion and rest; the latter exist in so far as they are comprehended, not only in the attribute Thought, but in God's infinite idea (E2p8c), as being actual parts of that immediate infinite mode. The equivalent, in Thought, of the eternal essence of a body is not only the eternal essence of the corresponding idea: it is the eternal idea of the essence of that same body. [verwijst naar Individu et Communauté chez Spinoza (1969), pp 574-6]
The difference between the status of ideas of non-existent bodies and that of their ideata, which Matheron ironically calls `slight' (peu), is momentous: there is all the difference in the world between possible existence in an attribute and actual existence in an eternal mode.
Spinoza himself contributed to the prevalent incomprehension of Ethics II, 8, by explaining less than clearly his own illustration of what he meant. Euclid has shown that, if A, C, F, and G are points on the circumference of a circle such that the lines AC and FG intersect at a point B within it, then the rectangle with base AB and height BC is equal in area with that of base BG and height BF (Elements III, 35w ) Spinoza comments:
So in a circle there are contained infinitely many rectangles equal to one another. Nevertheless, none of them can be said to exist except insofar as the circle exists, nor also can the idea of any of these rectangles be said to exist except insofar as it is comprehended in the idea of the circle. Now of these infinitely many [rectangles] let two only [viz. those formed from the segments of lines AC and FG; note: Replacing the single letters ‘D’ and ‘E’ by which Spinoza denotes the intersectinglines] exist. Of course their ideas also exist now, not only insofar as they are comprehended in the idea of the circle, but also insofar as they involve the existence of those rectangles. By this they are distinguished from the other ideas of the other rectangles. (E2p8s G II, 91 / 18--28)
The clue to understanding this passage is that, according to Spinoza's theory of ideas, you understand a sentence by actually having the ideas it expresses, not by possibly having them. Thus, you cannot understand its first sentence, 'In a circle there are contained infinitely many rectangles equal to one another', without having actual ideas of the possible rectangles formed by the segments of the lines cutting the circle and intersecting at a point within it.
If this clue is kept in mind, it can be seen that Spinoza is asserting: (i) that you cannot have an actual idea of the possible rectangles formed by possible lines cutting an actual circle unless that circle actually exists; for if it did not exist, your idea would be of rectangles formed by lines cutting a possible circle, not an actual one; (ii) that you can have an actual idea of the possible rectangles formed by possible segments of possible lines cutting an actual circle; for if you could not, theorems could not be proved about them; (iii) that for a reason parallel to that for (i), you cannot have an actual idea of an actual rectangle formed by segments of an actual line cutting an actual circle unless that line actually exists and is actually divided into two segments; and (iv) that when you have an actual idea of actual rectangles formed by actual segments of actual lines cutting an actual circle, your ideas of them exist both as ideas of essences (that is, of things `comprehended in the idea of the circle'), and as ideas of actual existents (that is, as ideas `involv[ing] the existence of those rectangles').
Although in Ethics II Spinoza does not apply to God's cognition of non-existent bodies what he has said about non-existent individuals generally, the application is evident. God, so far as he constitutes the idea of an actually existing human body, will have an idea of it both as comprehended in his infinite idea of nature as extended, and as involving the actual existence of that body. And when that body does not exist, whether before its conception or after its death, God will still constitute the idea of it: not as involving actual existence, but as comprehended in his actual infinite idea of nature as extended. Since, according to Spinoza, the mind of a living human being is identical with God's, so far as God's mind constitutes the idea of that human being's body and nothing else, it remains for him to inquire whether God's mind, so far as it constitutes the idea of the body of a human being who is dead or not yet born, and nothing else, is identical with the whole of that human being's mind, or only with part of it.
Volgt § 10.4. The Human Mind Without Relation to the Human Body. [pm]
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Mijn conclusie is: ik beschouw deze behandeling die Donagan geeft (met gebruikmaking van Matheron) als een duidelijke en betekenisvolle uitleg van wat Spinoza bedoeld moet hebben met ‘kennis van niet-bestaande dingen’. Er zit, zoals ik in het vorige blog ook al heb laten zien, geen spatje platonisme en ook geen leibnizisme in. Ik kan hier beter mee uit de voeten dan met wat Mogen Laerke ervan brouwde.
Correctie. In het blog van 29 juli 2015 distantieer ik me bij nader inzien van Donagan's lezing