I have enjoyed working with computers for most of my adult life, beginning with the programming of main-frames back in the late 1960s, and over the years we have all watched the size of the hardware decrease considerably while at the same time the complexity and performance of the circuitry has increased to where today's microprocessors are one of the most sophisticated machines that mankind has produced. At some point it occurred to me, and of course it had already occurred to many others, that we humans have been, in a way, building such machines as a crude reflection of our own mind/body with the programming perhaps reflecting the "mind" and the processor and input/output devices representing the "brain" with its attendant sense and muscle systems.

    Now that I have begun to study the brain and the rest of the human body mechanisms I see that even today's relatively more complex computers are like simple toys by comparison although, as Spinoza observed, all bodies, whether computers or brains, etc., share in common (see E2P13, Lemmas 1 and 2) that they do not exist in themselves but rather they exist in and are conceived through Extension (they are Modes of an Attribute of Substance, as Spinoza defines it, not what is generally imagined as "matter" contrasted with "space") and that they (bodies) are ultimately defined and determined by nothing other than motion and rest as the immediate Modes of Extension. All the changes of state within a computer come down to the motion and rest of its various parts including the gating of charges, allowing them to move from one place to another ("place" being determined by various other bodies relatively at rest), or at least to move, and affect movement in, neighboring parts.

    The extreme complexity of the brain/body and its states (the modifications of the body in Spinoza's terms) likewise always involve the relative movement of its parts such as the gating of ions into and out of the individual neurons and other cells through the various types of cell membrane channels, and, at times, there is an associated release of packets of one or another type of molecule moving into a synapse between two neurons. The ions and released molecules usually move individually by diffusion (involving the constant relative motion of the other "fluid parts" -to use Spinoza's description from E2Post5 or E2P17C) and those neurotransmitters, as the released synaptic molecules are called, affect various specific receptors in the membrane of the neighboring cell setting one or another complex chain of events into motion in that cell. And on it goes, as long as the body maintains a certain proportion of motion and rest among its various parts the continuing changes of state are endless and the body as a whole endures.

    But what about the mind? Spinoza defines what he means by "mind" as being the Idea (a Mode of the Attribute of Thought) which has for its object a Body (a Mode of the Attribute of Extension) and he writes such things as:

====== TEI-P33(33):
    A true idea (for we possess a true idea) is something different from its correlate (ideatum); thus a circle is different from the idea of a circle. The idea of a circle, is not something having a circumference and a centre, as a circle has; nor is the idea of a body that body itself. Now, as it is something different from its correlate, it is capable of being understood through itself; in other words, the idea, in so far as its actual essence (essentia formalis) is concerned, may be the subject of another subjective essence (essentia objectiva).[N2] And, again, this second subjective essence will, regarded in itself, be something real, and capable of being understood; and so on, indefinitely. For instance, the man Peter is something real; the true idea of Peter is the reality of Peter represented subjectively, and is in itself something real, and quite distinct from the actual Peter....
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[Note N2]: In modern language, "the idea may become the subject of another representation." Objectivus generally corresponds to the modern "subjective," formalis to the modern "objective."--[Tr.]
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...and in the Ethics:

====== E2: PROP. 11:
    The first element, which constitutes the actual being of the human mind, is the idea of some particular thing actually existing.
Proof...
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...and:

====== E2: PROP. 13:
    The object of the idea constituting the human mind is the body, in other words a certain mode of extension which actually exists, and nothing else.
Proof...
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    This may make it seem at first that Mind and Body are two completely separate things but Spinoza also explains that, if we think carefully about what he has expressed, this is not actually the case:

====== E3: PROP. 2, Note:
--This is made more clear by what was said in the note E2P7CN, namely, that mind and body are one and the same thing, conceived first under the attribute of thought, secondly, under the attribute of extension. Thus it follows that the order or concatenation of things is identical, whether nature be conceived under the one attribute or the other; consequently the order of states of activity and passivity in our body is simultaneous in nature with the order of states of activity and passivity in the mind. The same conclusion is evident from the manner in which we proved E2P12.

    Nevertheless, though such is the case, and though there be no further room for doubt, I can scarcely believe, until the fact is proved by experience, that men can be induced to consider the question calmly and fairly, so firmly are they convinced that it is merely at the bidding of the mind, that the body is set in motion or at rest, or performs a variety of actions depending solely on the mind's will or the exercise of thought....
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    Mind and Body only seem to be completely separate because, in part, our mind mistakes the ideas of the modifications of our own bodies for "external bodies" (and the ideas of them) while these are actually confused and inadequate ideas of our own body (see E2P19-P31). Much of this confusion, as Spinoza explains, has arisen because we did not acquire new ideas "in the proper order" and so by the time we begin to wonder about the nature of things like "external bodies" we are already wedded to our own particular confusions of our particular imagination and memory which we mistake for "reality" (see the Appendix to Ethics Part 1 for instance.) And so, Spinoza, after coming to understand things for himself, has the task of helping us to undo much of our confusion which we nevertheless do not at first see as confusion. While expressing his method of Improving the Understanding in the TEI he writes:

====== TEI-P43(38):
...if by some happy chance anyone had adopted this method in his investigations of nature--that is, if he had acquired new ideas in the proper order, according to the standard of the original true idea, he would never have doubted of the truth of his knowledge, inasmuch as truth, as we have shown, makes itself manifest, and all things would flow, as it were, spontaneously toward him. But as this never, or rarely, happens, I have been forced so to arrange my proceedings, that we may acquire by reflection and forethought what we cannot acquire by chance, and that it may at the same time appear that, for proving the truth, and for valid reasoning, we need no other means than the truth and valid reasoning themselves: for by valid reasoning I have established valid reasoning, and, in like measure, I seek still to establish it.
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...and, regarding our pervasive confusion involving words and images rather than adequate Ideas he writes in the Ethics:

====== E2: PROP. 49 Corollary, Note:
...I begin, then, with the first point, and warn my readers to make an accurate distinction between an idea, or conception of the mind, and the images of things which we imagine. It is further necessary that they should distinguish between idea and words, whereby we signify things. These three--namely, images, words, and ideas --are by many persons either entirely confused together, or not distinguished with sufficient accuracy or care, and hence people are generally in ignorance, how absolutely necessary is a knowledge of this doctrine of the will, both for philosophic purposes and for the wise ordering of life.

    Those who think that ideas consist in images which are formed in us by contact with external bodies, persuade themselves that the ideas of those things, whereof we can form no mental picture, are not ideas, but only figments, which we invent by the free decree of our will; they thus regard ideas as though they were inanimate pictures on a panel, and, filled with this misconception, do not see that an idea, inasmuch as it is an idea, involves an affirmation or negation.

    Again, those who confuse words with ideas, or with the affirmation which an idea involves, think that they can wish something contrary to what they feel, affirm, or deny. This misconception will easily be laid aside by one, who reflects on the nature of knowledge, and seeing that it in no wise involves the conception of extension, will therefore clearly understand, that an idea (being a mode of thinking) does not consist in the image of anything, nor in words. The essence of words and images is put together by bodily motions, which in no wise involve the conception of thought....
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    That last sentence may again seem to contradict the idea that Mind and Body are actually one and the same thing but the contradiction is only apparent from the viewpoint of our Imagination. Spinoza is in a tough spot since he is forced to use words which will at first necessarily be filtered through the existing associations of those words and images already present in the particular imagination/memory of his readers and of course the order and connection of these existing associations must differ for each reader.

    Things are further complicated, regarding Mind and Body, when Spinoza finally tries to help us to "see" for ourselves that the Adequate Ideas in the Mind (which are actually part of the Infinite Intellect of God --which is the immediate Mode of Thought, just as motion/rest is the immediate Mode of Extension) are Eternal and unchanging, having nothing to do with time and place (see E5P29 and Note). And, from the confused viewpoint of the Imagination, this seems absurd because "eternity" is only perceived confusedly by it as "endless time" (see E5P34C, Note), not as Existence itself following necessarily from (E1Def8), or actually being identical with (E1P20), the Essence of the One Substance.

    Nevertheless, to borrow a phrase from Spinoza, "I can scarcely believe, until the fact is proved by experience, that men can be induced to consider the question calmly and fairly" and I don't myself believe that the scientific method involving empirical observation, measurement, time, and number will ever itself convince anyone to...:

====== From the end of E5: PROP. 20, Note:
...pass on to those matters, which appertain to the duration of the mind, without relation to the body.
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...although such scientific endevours may "awaken" the mind and help it to "turn" in a different direction and to know itself and God directly:

====== E5: PROP. 30:
    Our mind, in so far as it knows itself and the body under the form of eternity, has to that extent necessarily a knowledge of God, and knows that it is in God, and is conceived through God.

Proof.-- Eternity is the very essence of God, in so far as this involves necessary existence (E1D8). Therefore to conceive things under the form of eternity, is to conceive things in so far as they are conceived through the essence of God as real entities, or in so far as they involve existence through the essence of God; wherefore our mind, in so far as it conceives itself and the body under the form of eternity, has to that extent necessarily a knowledge of God, and knows, etc. Q.E.D.
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