Substance. Reality itself.

This move distinguishes Spinoza from most other Western metaphysics. In Western metaphysics, most have tried to eliminate perspectives, to reduce the reality to one particular idea, entity or force, such that we can say by knowing this, we understand or experience the full extent of reality. More that, this method of "explanation" is considered the goal of metaphysical inquiry, to find the equation which predicts everything or the system which shows why consciousness is defined.

Spinoza is pointing out this metaphysical practice does not understand logic and its relationships to the world. It denies the limitation of perspective, proposing there is some way to reduce all to a single origin , which logically defines without any reference to the world itself. Since perspectives are distinct and unique (whether we are talking about a person, a cat, a rock, the finite, the finite), reduction to a single accounting side, entity or force cannot occur. In the presence of different perspectives, there are necessary many logical distinct definitions running parallel, within the same reality.

One cannot have the mind without the body and vice versa. To suggest mind without body fails because it turns the infinite of thought into a finite presence. On the other hand, to suggest a body without a mind is incoherent, as it would mean the body had no meaning or expression in logic.

To avoid incoherence, mind and body must be two perspectives of the same reality. They cannot be squished into one notion of origin or cause that accounts for everything. Unity must be an expression of perspectives (i.e. perspectives express Unity), rather than Unity being an an explanation of perspectives (i.e. Unity accounts for all perspectives).

That's obviously a ridiculous example. It's a more subtle matter than that. We simply don't know what the relationship between thought, emotion, desire and so on, as subjectively experienced and neural processes is; and probably never will, because the ways the two are experienced are so different.

That is just an opinion; you have no way of knowing that. — John

Actually, we do. The causal relationship of "thought" presupposes extension. Someone's thoughts causing events is entirely possible. What matters though is, under Spinoza's system, these thoughts are extension. If my thoughts cause an event, then finite states of existence, instances of my experiences, are doing the causing.

Thought as Spinoza uses it, unchanging logical meaning, what others might have called "form," is not causal. It doesn't exist. It's timeless. Meaning never changes or causes.

All you are saying boils down to the fact that we don't see minds without bodies; and that no bodies are seen at all without minds. Yes, that is the human situation. We try to imagine the independent existence of bodies without there being any minds, but it is always a mind imagining it; so we can't really do it; although we do mostly, in this scientific materialistic age, tend to think that bodies were around long before minds were there to enable them to appear. As to whether there can be minds without bodies; we simply don't and cannot know the answer to that because minds cannot be detected by the senses.

That's obviously a ridiculous example. It's a more subtle matter than that. We simply don't know what the relationship between thought, emotion, desire and so on, as subjectively experienced and neural processes is; and probably never will, because the ways the two are experienced are so different. — John

It's not ridiculous at all, it's simply the only plausible explanation for our experience as far as I can see.

All this relies on the unproven ( and I would argue, unproveable) hypothesis that thoughts are 'really' nothing more than physical events. I would say this is really nothing more than a prejudice which reflects the basic presuppositions of our scientific materialist age.

NO... it asserts just the opposite.

The point is thought not a physical event at all. It's not finite. It's unchanging. By the nature that is more than a finite event (it's timeless), thought cannot be causal. To suggest thought causes is to assert it is only a physical event-- nonsense.

(this is why instances of our experiences causing events are extension).

Well, I don't think any untestable explanation like that can rightly be thought of in terms of 'plausibility'. Plausibility is relevant only to hypotheses that we might think are verifiable or at least falsifiable. And even falsifiability is replete with problems if you take a look at some contemporary philosophy of science. As Hume noted what we think is likely or plausible really comes down to mere habits of thought.

As human noted what we think is likely or plausible really comes down to mere habits of thought. — John

That's if you believe Hume. I don't find that to be the case. I find that we believe something to be plausible when it is coherent.

If thought is not physical and it is yet real then there is something real which is non-physical. This brings us back to Descartes. The 'interaction' problem his philosophy is charged with, is itself based on the assumption that because we cannot conceive how the non-physical could interact with the physical that therefore the non-physical could not possibly interact with the physical. I think this assumption is nothing more than a prejudice due to ignorance.

It's not surprising that we cannot conceive of how the non-physical could interact with the physical because we understand causation in terms of energy exchange; in terms of the interactions of physical forces. Causation really, apart form our hypotheses concerning forces, is a matter of observed correlations. And we cannot directly observe correlations between thoughts and physical processes. We know there are thoughts at all only subjectively. My thoughts can never be observed by others; or even directly by myself; I know their existence only in the thinking of them.

Then why is there so much disagreement? The question is 'coherent according to who, or coherent with what set of presuppositions'?

Then why is there so much disagreement? — John

Because people never think about those things generally... And even when they do, many are still confused, not to mention that such things don't have much value in earning money and stuff that most people care about.

I am referring to disagreement among people who do think a lot about those things; disagreement among philosophers that is. Spinozism, for example, has not become the universally accepted metaphysical system by any means, even despite the fact that Descartes is currently out of favour and we live in a scientific materialist age. You might accept Spinozism, but do you really believe it is the ultimate answer and that you know better than all the contemporary philosophers who do not accept it, and do really believe their lack of acceptance of it is due merely to ignorance?

The interactions problem is born of Descartes thinking of thought as only physical. He takes what is physical, our existing experiences and proclaims them to be in infinite of thought.

In doing so, Descartes mistakes the infinite (thought), for finite human experiences (extension), leaving us with the "gap" of how we can be infinite ( have minds and experiences) when we are only finite (a body).

Our "minds (i.e. existing experiences)" were never thought. They are only finite states. We have our body (extension) and experiences/ "mind" (extension) interacting as finite casual states. We were always a mind (extension) and body (extension). There is no non-physcial interaction with our bodies to resolve all explain. It's an illusion generated by Descartes' misunderstanding of human minds and thought.

You are misinterpreting Descartes if you think he believed thought is physical. Textual evidence for this claim?

It's a base claim of his philosophy- he doesn't distinguish between meaning (the infinite of thought) and the existence of experiences (existing minds). He equates these as the substance of "Mind" or "consciousness."

My point here is not that Descartes thinks mind is "only physical" in those words, but rather he equates the physical (existing experiences) with an infinite (thought), forming a system where thought is understood to be equivalent to existing experiences.

I am referring to disagreement among people who do think a lot about those things; disagreement among philosophers that is. Spinozism, for example, has not become the universally accepted metaphysical system by any means, even despite the fact that Descartes is currently out of favour and we live in a scientific materialist age. — John

Do you think for example that Descartes is unfairly out of favour today?

Spinozism, for example, has not become the universally accepted metaphysical system by any means, even despite the fact that Descartes is currently out of favour and we live in a scientific materialist age. — John

Well most philosophers earn their money based on the diversity of their research. If Spinozism became the only accepted position, there'd be a lot less opportunities for publication...

Do you think for example that Descartes is unfairly out of favour today? — Agustino

I think Descartes is often unfairly maligned and undervalued as a philosopher. Personally, I am not a fan of substance dualism; but then I am not a fan of any substance ontology at all; as you may have gathered.

What I will say is that we are faced with two kinds of phenomena, two spheres of experience; the mental and the physical. The first is known from the so-called first person perspective and the second from the so-called third person perspective. We have reasons to believe that thoughts interact with (their own) bodies, although we can't be sure whether there is really any interaction or only some kind of "parrallelism" (pace Leibniz or Spinoza). Or perhaps the physical is an expression of the spiritual (this position is not necessarily any form of idealism, by the way).

We can only grope and intuit when it comes to these kinds of questions, because they are not really subject to empirical investigation. It comes down to taste, as I see it; there are no demonstrably correct answers, and every formulation is probably inadequate anyway.

I don't think the real task of philosophy is to answer these kinds of intractable questions anyway, but to get out from under the influence of them. It doesn't really matter what you believe about metaphysics; you can live an equally good life regardless.For that something else is needed; which cannot really be spoken about. I believe it consists in intuition, in ethical, aesthetic, religious and spiritual feeling, which is to say, faith and experience, and the activity those kinds of faith and experience lead to.