If I were to choose between the three most celebrated 17th Century rationalists, Descartes, Spinoza or Leibniz, Spinoza would be my hands-down favourite. Not so much because of his Stoicism, but more because of his holism—as distinct from Leibniz’s Monadology or Descartes dualism.
For Spinoza, there is only one substance whose essence explains its existence: Nature. Of course, poor old Baruch got in trouble by forwarding a pantheistic notion of God not as some unknowable transcendent being separate from nature, but rather as knowable and coextensive with nature—or as Karl Jaspers describes it God not as passive, but God as nature in action! Spinoza argued, contra Descartes, that if God were not co-extensive with nature, but instead something apart from it or ‘above it’ then there would be at least one thing that God was ‘not’—namely nature. But God (to be God) must be everything or infinite, not limited or finite. If God is not infinite, if something exists outside of and distinct from God (i.e. nature) then God has boundaries—a contradiction. A rather neat little argument!
Now, of course, as somewhat of a skeptic where the existence of God is concerned, the notion of nature as a divine unity is not an idea I would unhesitatingly accept, even though, as definitions of God go, this one is rather more palatable than the Judeo Christian or Islamic ones. How so? Well, if God is in nature, then nature is ‘perfect’ and beautiful in a way that inspires wonder, admiration and awe. This is a rather more reasonable and ecologically sustainable notion of God/Nature than that of the Judeo-Christian God who creates human beings and then encourages them to dominate and subdue nature! Unfortunately, it is the latter conception of God that prevails, and we are the worse for it. There is also something attractive about Spinoza’s monistic approach to understanding the human mind or consciousness. Consciousness (mind substance) and matter (material substance) are, for Spinoza, not radically distinct and, therefore, incompatible but simply attributes or aspects of the whole or the oneness of nature—there is no mind/body dichotomy here. Neither is there any notion of a 'personal' God--an idea that is as self-aggrandizing and narcissistic as it is ridiculous. As if we knew God in such an intimate way that we communicate with him and are certain he is in the least bit interested in what we do or think! Wow--what colossal arrogance, what unmitigated gall! To Spinoza it would be like saying if we love nature, it should love us back!
Now one might argue that Spinoza’s rationalist system which begins in the Ethics with a number of assumptions (definitions and axioms) and then proceeds to deduce from these an entire ‘metaphysics’ of the universe would ends up denying the possibility of free will. However, Spinoza would argue that there just is no such thing as an absolutely ‘free’ will if this means an uncaused cause or spontaneous thought or action. To assume we are free in this sense would, once again, place us outside or above nature. If it sometimes appears that we have made a ‘free’ or spontaneous decision, it is only because we have yet to pinpoint the cause. But what then of ethics? Is not the fundamental presupposition of ethics that we are free do otherwise? Does not ‘ought’, as Immanuel Kant might say, imply ‘can’—or put simply, is it not the case that if we say someone is morally obliged to perform a certain action, we also say that, being a free agent, he or she may refuse to do so? If we are not free to choose, then our actions must be compelled by something outside of us. If this is the case then ethical thinking and actions drop out of the picture.
However, Spinoza’s Ethics tell a rather different more nuanced story about human freedom and compulsion. The notion of what is required to be a good person is not primarily about possessing a freedom outside or in contradistinction from nature. Many writers on ethical conduct and goodness presuppose this. However, in so doing the latter,
… appear to conceive man to be situated in nature as a kingdom within a kingdom: for they believe that he disturbs rather than follows nature's order, that he has absolute control over his actions, and that he is determined solely by himself. They attribute human infirmities and fickleness, not to the power of nature in general, but to some mysterious flaw in the nature of man, which accordingly they bemoan, deride, despise, or, as usually happens, abuse: he, who succeeds in hitting off the weakness of the human mind more eloquently or more acutely than his fellows, is looked upon as a seer. (Part III On The Origins of the Emotions)
But the reality is that neither human mind nor body exist outside of nature or nature’s influence. It is the ultimate in human arrogance and hubris to assume otherwise. That does not mean that we are not ethically responsible for becoming a certain sort of person or for governing our lives in ways that respect nature and prevent us from being dominated and enslaved by our passions. For example, when we are induced to act from causes such as hatred, anger, contempt, envy or pride (what Spinoza calls passive emotions) we act out of compulsions that are literally ‘thoughtless’.
By contrast, when we act from understanding and knowledge, when we think before we act, our ethical agency is empowered and we are less governed or seduced by the ‘dark side’ to borrow the Star Wars phrase. Put in Spinoza’s language, as critical thinking and knowing beings we become the adequate cause of our thoughts and actions. As a result, we tend to cultivate in ourselves a certain temperance or moderation in all things, and refuse to be the sort of person who is enslaved, pushed or shoved by outside causes. There be stoicism here. But it is not so much austere as it is liberating. We are indeed part of nature—like all sentient forms of life we are striving (conatus) beings subject to cause and effect, but as speaking, thinking and knowing beings we are also capable of becoming critically conscious of and responsible for what we do to ourselves, to others and to the world. We not only have the have the ability to know others and therefore ourselves, but we have the capacity to love others, to love nature (God) and finally, to love ourselves. Most importantly, when we are able to discover or come to know the dark forces that compel us to act in irresponsible, thoughtless or unethical ways, we exercise our freedom in a robust way by resisting them--in much the same way one can be freed from the dark forces of the unconscious mind by making them conscious through psychoanalysis, or so Freud would argue 200 or so years later.
What I find very attractive about all of this is Spinoza's idea that it is not nature we must subdue and control, it is...ourselves!