Baruch Spinoza is a puzzle and a wonder. Living mostly in Amsterdam in the mid 17th century (1632 - 1677), excommunicated from his Jewish community for his "evil opinions, abominable heresies and monstrous deeds", shunned by most of the era's intellectual elite, he supported himself modestly by fashioning lenses for telescopes and eyeglasses while on a solitary deep dive into human nature, God and religion, psychology, political theory and ethics. During his all too brief lifetime, he lived by the motto Caute! (caution), anonymously publishing only two books, Descartes Principles of Philosophy and the Theological-Political Treatise, which was immediately denounced by religious leaders as "a book forged in hell". The quality of his insights, developed from rigorous and fearless examination of things as they are and informed by careful study of the works of classical philosophers, religious thinkers and recent predecessors (Descartes) and contemporaries like Hobbes and Leibniz, make him seem more than an outlier. He is a unicorn, in fact, a thinker as bold as Plato, Newton, Galileo, Darwin, Einstein or Bohr. Michael Della Rocca pays tribute to Spinoza with a detailed and sympathetic presentation of his ideas. Spinoza is far from an easy read but, for me, Della Rocca's book made the the main lines of his inquiry accessible. This is important; I have usually found philosophy difficult to read in the original. I have taken a run at a translation of Kant's Critique of Pure Reason but took no pleasure in the structure of his writing. And I also admit that reading Spinoza in translation (he wrote his works in Latin, probably to make them less accessible to a lay audience) was difficult and frustrating. So I am grateful to Della Rocco for finding a middle ground that respects the intricacy of Spinoza's work and contains a fine sense of debate about the usefulness of some of Spinoza's claims. The unifying concept of Spinoza's philosophy is the Principle of Sufficient Reason (PSR), the idea that nothing is uncaused and everything can be intelligible, though humans, as limited beings, may not have sufficient knowledge of sensory power to understand all things. "It would be impossible for human weakness to grasp the series of singular, changeable things, not only because there are innumerably many of them but also because of the infinite circumstances in one and the same thing." Spinoza's unreserved embrace of reason led to his commitment to naturalism, the idea that in nature there is only one set of rules, at all times and in all places. There are no miracles, no events that are by their nature inexplicable, though we may not be able to explain them in our time and place. He refuted all philosophers and all religious thinkers who conceived of "man in Nature as a dominion within a dominion. For they believe that man disturbs, rather than follows the order of Nature." Spinoza lived at a time of great religious unrest. Vicious European wars were fought over religious dogmas of the Catholic and Protestant churches. People were executed in unspeakably cruel ways for the sin of heresy. Spinoza's concept of God was utterly heretical for its times. In Spinoza's system, there was no transcendent God with any interest in individual beings. That would be an inexplicable brute fact, akin to the rejected idea of of a dominion within a dominion. "There is only one substance and it is God" seems to be the fundamental starting point for his inquiry. Spinoza's way of expressing this concept was Deus sive Natura, God or Nature. Everything that exists, substance and thought, laws and forces of nature, is an attribute of God or Nature. He viewed the bible as a collection of fables and historical stories with power to inspire but with no divine status. The old testament could be seen as wisdom literature containing rules and laws for individual and societal governance. The new testament, in his view, brought into prominence "true piety" which consisted of "loving your neighbour as yourself". Spinoza's naturalism enabled him to interpret ancient philosophical questions in new ways. Descartes, motivated by the theological need to create a basis for the immortality of the soul, which he equated with the mind, saw duality between mind and body (thought and extension). Spinoza saw things in more systemic terms. The mind could be viewed as the brain's idea of the body, a view much closer to the modern concept favoured by neurobiologists. Spinoza's psychology is based on his notion of the essence of being which he identified as a "striving to persist" or "conatus". This essence is a feature of all living things, not privileged to humans alone. Desire is the expression of striving. Spinoza saw all behavior as essentially egotistic or self preserving. Humans strive not only to persist but to increase our power of acting. Thus, human activity is based on the dynamics of power, a notion closely allied with later philosophical thinking such as "the will to power" central to Nietzsche's system. Della Rocca writes "there can be no desire that is totally divorced from our self interest - in particular there can be no desire to do something particularly because it is the right thing to do." From this central principle of striving to exist, emotions can be understood. Joy is a being's passage from a lesser to a greater perfection (or power of acting) while sadness is a being's passage from a greater to a lesser perfection. Spinoza was an arch rationalist in the sense that he believed that everything could be explicable with enough knowledge. However, in Spinoza's system, reason alone cannot control emotion or desire. That may seem to contradict the rules of rationalism. Desire can be controlled only, in Spinoza's view, by a stronger desire. My strong desire to eat the apple pie sitting on the kitchen counter may be countered by my stronger desire to be fit and disciplined, consistent with the story I tell myself about my nature. In the parallel realm of substance, Spinoza believed "there is no singular thing in nature than which there is not another more powerful and stronger. Whatever one is given, there is another more powerful by which it can be destroyed." (He would except his notion of God or Nature from this assertion since the hierarchy of singular things are simply modes or inadequate expressions of the one substance of God or Nature.) Spinoza's approach to ethics has the virtue of simplifying some ancient philosophical questions. Della Rocca notes that any ethical theory must provide not only an account of the good but also an account of the right, of what we are morally obligated to do. Spinoza, he says, holds that an action is good to the extent that it increases the agent's power and bad to the extent that it decreases the agent's power. Further, what is right to do is what is good to do. But, one might object, in Spinoza's system of desire, self interest and power, how would humans ever live together in peace? In the condition where each individual attempts to exercise her rights against all others (to increase her power of acting), human life, in Spinoza's words "must necessarily be most wretched.", an echo of Hobbes' "nasty, brutish and short" dictum. To that objection, Spinoza would offer two ideas. First, at the level of an individual, is very often in our self interest to help others; in fact, he would probably say that to live within the single dominion of nature, the desires for respect, belonging and community, desires that lean toward increasing an individual's power of acting, lead people to do the right thing with others. Second, at the level of human groups, the right to increase one's power of acting must necessarily be viewed in the long run. For Spinoza what is good for us to do and what we ought to do is acquire knowledge. That leads us toward morality. While individual rights stem from our nature as individuals striving for self-preservation, we soon gain the knowledge that we can't achieve much of value on our own, especially in the long run, and thus we agree to pool our rights and work harmoniously from our common interests and refrain from harming one another. Spinoza uses the term "sovereign" for this pooling of individual rights leading to his political philosophy described in The Theological-Political Treatise and his posthumous works, the Ethics and the unfinished Tractatus Politicus. Spinoza argued that the "sovereign", or government, must always be superior to religion. Though logically derived from the premises of his system, Spinoza no doubt drew practical conclusions from the first hand evidence he witnessed in his era where the contest of religious dogmas resulted in warfare and cruelty. This is the early enlightenment expression of separation of church and state but goes much further by explicitly favouring supremacy of the state. The wise sovereign will protect the freedom of citizens to philosophize and debate but will not tolerate actions inimical to its authority. Later thinkers found problems with this formulation as it seemed not to extend enough individual freedom to influence the rule of the sovereign. If he could, Spinoza would probably respond to these criticisms with arguments around degrees of freedom - the sovereign should be influenced by dissent that favours it's continuation in the long run. And it is important to note that Spinoza saw an important role for religion because of the power of its stories to motivate "true piety" in the mass of citizens- loving your neighbour as yourself. In intellectual realms as different as human nature, government, psychology, scriptural interpretation and ethical theory, Spinoza offers us much. He seems to have been a truly kind and gentle person; those who met him and called him friend, praised his character. One of my bucket list items is to visit his modest house in Amsterdam, preserved as a kind of shrine to this most humanistic of philosophers. His insights were subtle, audacious and often difficult to grasp. He was a wonderful fountain of wisdom of the early enlightenment and well worth careful study. As he wrote, "All things excellent are as difficult as they are rare."