Spinoza began as a follower of Descartes. He wrote at least one book on Cartesian philosophy. Thus, his thought makes more sense when viewed through a Cartesian setting. But, it is still the most original, and to some the most perfect approach to a purely rational description of the world determined purely through reason. And too, he was post-Galilean to the point that his ideas depend on and explain the role of natural physical laws in the universe. Consider for a moment what natural physical laws tell us. They tell us that interactions between things and events are determined by something natural to the things and the events and nothing else. The Stoics taught that the best life was that in harmony with nature. But they freely admitted they did not understand nature. Spinoza taught that all life was determined by nature, that what is could not be different and still be what is. As a brilliant young Jewish student in seventeenth century Amsterdam he was expected to be a great rabbi. However, his ideas seemed to the Jewish fathers of Amsterdam to be stepping sufficiently beyond the bounds of discretion that they would very likely endanger the Jewish colony. Thus first he was forbidden from speaking out and, since this had no effect, he was excommunicated from the Church. Considering the sense of scientific physical laws as applying directly to what is regardless of why it is or where it is going, he could not understand how it could be possible to think other than he did and still remain within the bounds of reason.

Spinoza developed a thorough metaphysical description of a dynamic universe that, more than any one else in his day, took into consideration the full import of scientifically developed natural physical laws. Consider, for a moment, that though natural laws as knowledge tokens can be considered to exist in another world. That is they are not created, and they are not sensed. They are discovered through reasoning on the events that involve physical entities, not on the entities themselves. They are abstract entities but they do not apply to abstract entities. They only apply to things that exist, that are. So Spinoza began his discussion of the nature of the universe by referring to what is. To being as a whole. We know that something is, and that it is what it is, rather than something else through its attributes. Thus, being, or as he liked to call it, substance, is the absolute totality of attributes. If we can know that a thing is and that it is what it is only through its attributes, and if substance is the totality of attributes then there can be only one substance and that substance must be the cause of all that exists. Therefore that substance must be God.

For a logical proof of what he maintained. Spinoza turned back to the methods developed by Euclid, by applying methods developed in Geometry to metaphysical arguments. He began with a set of definitions

I. Self-caused; That of which the essence involves existence.

By this he meant that anything that includes within its essence its own cause could not not exist. Since God is the only thing of which its essence involves existence, only God is self-caused.

II. Finite after its kind; Anything that can be limited by another thing of the same nature.

For example, body can be limited by body. Body is finite because we can always conceive of another greater body. Thought too is finite because it can be limited by thought. However, Body can not be limited by thought nor thought by body. In Descartes philosophy body was corporeal and thought incorporeal thus one could not act directly on another. But with Spinoza the question of corporeality never arises because thought and body are simply two different attributes through which we experience the world. They do not affect each other only because they are simply two different ways of looking at the same things.

III. Substance; that which is in itself, and is conceived through itself.

Aristotle's conception of substance was anything that we could talk about as an individual thing. Descartes applied the concept substance to anything on the single basis that they existed. Corporeal substance indicated the existence of bodies and incorporeal substance of thoughts. To make the concept more precise Spinoza used the term to designate only that of which a conception can be formed independent of any other conception. This implies that a substance cannot be conceived in relation to another substance otherwise their would be a connection between them and the two together would form a third substance. If we added additional substances the problem would multiply until we soon each the point of infinite regression. Therefore their can only be one substance, it must have as part of its essence its own existence, it must be God.

IV. Attribute; that which the intellect perceives as constituting the essence of substance.

Since attributes are what determine what a substance is, then they are in fact what the substance is. Since the one substance, God, has an infinite number of attributes because being all that is, all attributes must be attributed to him, God is everything that is possible to be. However, we as human beings can only experience God, the universe around us, through two attributes. The attribute of extension or body, and the attribute of thought. At this point he has succeeded in absorbing the ideas of Descartes and the traditional Aristotelian concepts of substance into a new concept that includes both but extends both to their logical conclusion.

V. Mode; those modifications of substance that are conceived through or exist in something other than themselves.

Since there is but one substance containing every possible attribute, then whatever else exists must be a modification, or mode, of that substance and must exist in and through that one substance. Thus everything that we conceive as existing must do so as a mode or modification of Gods existence. Since everything that exists in the universe is a mode of God's existence, we experience things through the two attributes of God that are accessible to us, thought and extension. With this definition he has overcome the basic Platonic problem of the meaning ot "participation."

VI. God; a being absolutely infinite.

This definition ties together God and substance. Since anything absolutely infinite must have existence as part of its essence and must necessarily contain all attributes.

VII. Free; that which exists solely by the necessity of its own nature.

The nature of something is its essence. A thing must be determined either by its own essence or by means of something external to it. To the extent that nothing external to a thing determines its existence that thing is necessarily free. Spinoza denies free will because that would imply that something could will that it be something other than it is by its own essence. However, he does make everything free to the extent that the essence of a thing, or what it is to be that thing, is determined entirely by forces internal to it. God and all of his creations thus are free to the extent that they exist solely by what they are, their essence.

VIII. Eternity; existence itself, that which is conceived necessary through being eternal.

These definitions form the starting point of his logical argument. What a definition does, in the Euclidean sense, is to put a name to a concept that can be found in intuition. They tell us what it is the author means when he uses the term. In themselves they are neither proofs nor proven. Axioms, on the other hand are logical derivations implied strictly by intuition. Thus axioms are considered self-evident in a different fashion than definitions. They are true expressions because we cannot conceive of them as being untrue. To make his argument Spinoza proposed the following axioms.

I. Everything which exists, either exists in itself or in something else.

This an excellent example of an axiom because to deny it is to deny either the way we use the English language, or the basic concept of rationality itself. Note how each of the following axioms also are such that their denial results in a contradiction.

II. That which cannot be conceived through anything else must be conceived through itself.

III. From a given cause an effect necessarily follows; and, on the other hand, if no definite cause is granted, it is impossible that an effect can follow.

While axiom II requires some thought before one can realize that it's denial is a necessary contradiction, axiom III is really an assumption. Still, it is an assumption that would never be denied in the seventeenth century, and it would not be denied even today by most people. Nevertheless, it is still an assumption. It wasn't until David Hume a century later that the assumption was questioned.

IV. The knowledge of an effect depends on and involves the knowledge of its cause.

This axiom is an implication from axiom III. It is essential for an understanding of axiom V. these constitute the essence of pure knowledge.

V. Things which have nothing in common cannot be understood, the one by means of the other; the conception of one does not involve the conception of the other.

This makes sense if you accept the idea that understanding something implies understanding its cause. therefore if the conception of one thing requires the conception of another there must be a relationship between their causes. In fact part of the cause of one of them must include the cause of the other. Therefore they are simply different varieties of the same thing.

VI. A true idea must correspond with its ideate or object.

VII. If a thing can be conceived as non-existing, its essence does not involve existence.

Note that this set of axioms underlies a very specific and detailed way of looking at the universe. All are developed entirely from pure thought.

Spinoza's definition of substance leads necessarily to the conclusion that there can not be more than one, using arguments similar to Parmenides argument for all being as a one. As a result this substance and God are one and the same. But his development of a concept of God differs from all of his predecessors because his idea of God, and those attributes through which he exercises his powers, are dynamic in themselves, and not simply the end-results of some series of logical exercises. . T. M. Forsyth explained this dynamism in a way that makes it more understandable.

Putting together the several strands of Spinoza's philosophy one sees that, whatever may be its deficiencies of logic and method, its essential import is not in doubt. What it teaches is that it is of the very nature of the infinite and perfect being to be manifest in finite individuals who can seek and find their true good in union with their immanent cause and enda union which is at the same time that of each with all. This relation of the finite and the infinite implies that the divine activity creating, sustaining and controlling all things is not that of a mere external power and compulsion but rather the inspiring and persuasive power of infinite love. The response of the finite individual has as its highest level the character of a rationally grounded and disinterested "love towards God," as the supreme reality made manifest in the whole universe of being. Thus the movement or process of the finite towards the infinite and the boundless self-giving of the infinite to the finite are one and the same fact. As the theologian expresses it, "Our opening and his entering are one moment."

This dynamic view of the universe is particularly important to our analyses of Spinoza's philosophy because during the period in which he lived physical laws were expressed in terms of motion. The notion of kinetic energy, the energy stored in every object by the law of gravity, was developed by Newton in the next generation. Thus God is what is, has infinite attributes, and everything that exists is a modification of God. As human beings we are aware of God and his modifications through only two of his infinite attributes, thought and extension. So when we perceive something through our senses we perceive it through the attribute of extension and when we perceive it through our mind we do so through the attribute of thought.

Since God is what is, that is nature, and since all that exists does so as a modification of God. Everything that exists must do so through its own nature. This is an important distinction because for Spinoza to be free means only to exist in ones own nature. The concept of free will from this point of view is simply inconceivable. There can be but one possible world because it is entirely determined through natural laws which are simply characteristics of God. This idea posed some problems for Spinoza's followers because it would seem that the denial of free will would lead to fatalism and deny man the opportunity to become good. But . Spinoza denied this making virtue in fact an expression of man's activities through the use of reason.

A free man is one who lives under the guidance of reason, who is not led by fear, but who directly desires that which is good, in other words, who strives to act, to live, and to preserve his own being on the basis of seeking his own true advantage; whereupon such a one thinks of nothing less than of death, but his wisdom is a meditation of life.

If we think back to Aristotle and his idea that happiness is activities of the soul in accordance with virtue, then we should be able to note the Aristotelian influence here. Aristotle's concept of soul was the essence of something that was alive. For man, his nature was to be rational. Therefore for Aristotle man reached the zenith of his happiness through rational actions that resulted in increasing his own virtue, or the value of his soul. Spinoza simply expressed it differently. . Spinoza said that Pleasure and pain were determined by the relationship between a man's actions and his own nature. Pleasure being derived from acting according to ones own nature, and pain from acting against ones own nature. Thus actions according to ones nature both bring pleasure and at the same time bring him to greater perfection.

As reason makes no demands contrary to nature, it demands that every man should love himself, should seek that which is useful to himI mean, that which is really useful to him, should desire everything which really brings man to greater perfection, and should, each for himself, endeavor as far as he can to preserve his own being. This is as necessarily true, as that the whole is greater than the parts.

Again, as virtue is nothing else but action in accordance with the laws of ones own nature, and as no one endeavors to preserve his own being except in accordance with the laws of his own nature, it follows, first, that the foundation of virtue is the endeavor to preserve ones own being, and that happiness consists in man's power of preserving his own being; secondly, that virtue is to be desired for its own sake, and that there is nothing more excellent or more useful to us, for the sake of which we should desire it; thirdly, and lastly, that suicides are weak-minded, and are overcome by external cause repugnant to their nature

No philosopher took reason to its limits like Spinoza. Yet, of all of the philosophical systems his is most in line with modern cosmology, to that of our modern physicists like Albert Einstein, Stephen Hawking, or Roger Penrose. Yet he lived and wrote during the earliest years of the birth of modern science. His ideas were objected to strenuously by the religious leaders of the day. He was labeled an atheist because his concept of God was different from that of established religion. The man who attempted to bring rationalism back into the mainstream of religion was Leibniz.