Western philosophy in the 17th and 18th centuries is divided between British empiricism and continental rationalism.
These theories are concerned with Epistemology (philosophy that investigates the origin, nature, methods, and limits of human knowledge).
Descartes, Leibniz and Spinoza were rationalists. They believed in pure reason, the mind alone, or at least the pre-eminence of the mind.
Descartes (31 March 1596 – 11 February 1650)
Descartes is considered the founder of modern philosophy. Bertrand Russell describes in his book, ‘A History of Western Philosophy’, a ‘freshness’ about his work that is not to be found in any previous philosophers since Plato: Descartes writes, not as a teacher, but as ‘a discoverer and explorer, anxious to communicate what he has found’.
Russell describes his style as ‘easy and un-pedantic’, addressed to intelligent men of the world rather than to pupils. Moreover, he has ‘an extraordinarily excellent style’ and an ‘admirable literary sense’.
Descartes held views in common with philosophers such as Galileo and Bacon. He was a sincere Catholic, and wished to persuade the Church in its own interests as well as in his to be less hostile to modern science than it showed itself in the case of Galileo. Like Bacon, Descartes compared knowledge to a tree, but for him the tree’s roots were metaphysics, its trunk was physics, and its fruitful branches were the moral and useful sciences. Descartes opposed Aristotelianism and the traditional education available in the universities:
“I had gained nothing but an increasing recognition of my ignorance.”
So far as pure philosophy is concerned, Descartes’ two most important books are:
1. The Discourse on Method (1637) and;
2. The Meditations (1642).
In these books Descartes begins by explaining the method of Cartesian doubt. ‘Method of doubt’ (or Cartesian doubt) involves the elimination of all interpretations of experience that are not absolutely certain. It was used as a method of deriving axioms upon which to base theories. Using this method, Descartes is able to raise doubts about everything except his mind so everything else even his body must be something else, some other kind of substance. The mind is one thing and the body another. This is Cartesian dualism.
There are two key ideas that are presented in the Discourse and elaborated in later works:
- Human beings are thinking substances.
- Matter is extension in motion.
Everything in his system is to be explained in terms of this dualism of mind and matter.
Descartes’ epistemology sets off a tendency in European (‘German’) philosophy called idealism – used by philosophers such as Kant and Hegel.
‘I think, therefore I am’ is Descartes’ famous Cogito, ergo sum. Anthony Kenny describes in his book, ‘A New History of Western Philosophy’, how this theory ‘prevents systematic doubt from leading to scepticism’ and Russell describes how it created the process by which is reached “Cartesian doubt,” ‘regretfully’.
To prevent his Cogito collapsing into solipsism, he needed to establish two things:
- that God exists;
- that God wouldn’t deceive us.
Ideas seem to be of three sorts: (1) those that are innate, (2) those that are foreign and come from without, (3) those that are invented by me.
Russell describes Descartes’ proofs of the existence of God as ‘not very original’; in the main they come from scholastic philosophy and that they were better stated by Leibniz.
Descartes’ Key Argument
God must have given us the idea of him –a trademark, a logo – when he created us. God is a benevolent being and therefore wouldn’t deceive us.
The Ontological Argument
This is a priori argument for God’s existence. God is a perfect being so he therefore exists – he would not be a perfect being if he didn’t exist.
Once it has been established (to Descartes’ satisfaction) that God exists and that he wouldn’t deceive us, Descartes then starts to reconstruct his beliefs.
Those that followed Descartes were Locke, Hume, and Kant who each offered their philosophies as new creations, constructed for the first time on sound scientific principles. Kenny wrote that, ‘Read my work, and discard my predecessors’ is a constant theme of seventeenth and eighteenth century thinkers and writers.
Spinoza (24 November 1632 – 21 February 1677)
Spinoza argues that if the world is separate from God then he has boundaries, so for God to be infinite he has to be part of the world.
Therefore there is only one substance (not two like Descartes said) and this was God. This is known as monism as opposed to dualism. This means that all of our thinking has a physical manifestation, and God (or nature) is the true substance.
Spinoza doesn’t believe in free will as humans are simply aspects of God. Pantheism is the belief that everything composes an all-encompassing, immanent God, therefore Spinoza’s argument is a type of Pantheism. To put it more simply: God did not create nature, God is nature and people are aspects of God. This means that everything that happens is simply a manifestation of God so this therefore eliminates sin and evil.
In philosophy the seventeenth century was the age of the revolt against Aristotle. Kenny believes this revolt is carried to its ultimate length by Spinoza.
The hallmarks of Aristotelian scholasticism are the distinctions it makes and the pairs of concepts with which it operates to explain human beings and the material world: actuality and potentiality; form and matter; disposition and activity; intellect and will; natural and rational powers; final and formal causes. All these distinctions are collapsed by Spinoza and his philosophy is often regarded as the most extravagant form of rationalism.
Spinoza took over and enlarged Descartes’ set of definitions and axioms, and proved fifty-eight propositions, of which the first is :
- ‘we can be absolutely certain of nothing, so long as we do not know what we ourselves exist’, and of which the last is;
- ‘if a particular body A can be moved in any direction by a force however small, it is necessarily surrounded by bodies all moving with an equal speed’.
Spinoza moved away from Descartes’ philosophy of mind and did not believe that the intellect and the will were distinct from each other, and that human beings enjoyed the degree of freedom which Descartes attributed to them.
Russell describes Spinoza’s political theory is, in the main, derived from Hobbes, in spite of the ‘enormous temperamental difference between the two men’.
Spinoza’s Ethics sets out his own system in the way he had earlier set out Descartes’, on the model of Euclid’s geometry. It is in five parts: ‘Of God’; ‘Of the Nature and Origin of the Mind’; ‘Of the Origin and Nature of the Passions’; ‘Of Human Bondage’; and ‘Of Human Freedom’. The last two books, of which, are believed by Russell to be the ‘most interesting’. We are in bondage in proportion as what happens to us is determined by outside causes, and we are free in proportion as we are self-determined. Spinoza, like Socrates and Plato, believes that all wrong action is due to intellectual error: the man who adequately understands his own circumstances will act wisely, and will even be happy in the face of what to another would be misfortune. Spinoza’s outlook is intended to liberate men from the tyranny of fear.
Russell describes Spinoza as ‘the noblest and most lovable of the great philosophers’. During his lifetime and sometime after he was considered a man of appalling wickedness. Interestingly, Leibniz, who owed much to him, concealed his debt, and carefully abstained from saying a word in his praise; he even went so far as to lie about the extent of his personal acquaintance with the heretic Jew.
Leibniz (July 1, 1646 – November 14, 1716)
Leibniz crossed the boundary between the seventeenth and eighteenth centuries. He surmised that there are indefinitely many substances individually programmed to act in a predetermined way, each program being coordinated with all the others. True substances were explained as metaphysical points which, Leibniz asserted, are both real and exact. A Monad is Leibniz’s word for substance: “What ever is complex is made up of what’s simple”. These are simple, non-divisible, soul like entities which lack extension or any physical characteristics.
In simpler terms:
- everything that is complex must be able to break down into simpler elements until you get to the 100% genuine simple not analysable elements of matter.
These things cannot be material as they cannot be extended and extension is always divisible, so the ultimate constituents of reality must be immaterial and not occupying space.
In 1676 Leibniz visited Spinoza in Amsterdam and studied the Ethics in manuscript, writing substantial comments. But after the Ethics had been published, and Spinoza was a target of general obloquy, Leibniz played down their former intimacy.
It was in the winter of 1685 that Leibniz wrote the first of his works which became lastingly popular, The Discourse on Metaphysics.
Characteristics of his doctrine:
- We live in the best of all possible worlds, a world freely chosen by God who always acts in an orderly manner according to reason. God is not, as Spinoza thought, the only substance: there are also created individuals.
- The human mind contains, from its origin, the ideas of all things; no external object, other than God, can act upon our souls. Our ideas, however, are our own ideas and not God’s. So too are the acts of our will, which God inclines without necessitating, God conserves us continually in being, but our thoughts occur spontaneously and freely. Soul and body do not interact with each other, but thought and bodily events occur in correspondence because they are placed in liaison by the loving providence of God.
Russell believes Leibniz to be one of ‘the supreme intellects of all time’, but unlike Spinoza, as a human being he was ‘not admirable’. This is because he was supposedly destitute of those higher philosophic virtues that are so notable in Spinoza.
Like Descartes and Spinoza, Leibniz based his philosophy on the notion of substance, but he differed radically from them as regards the relation of mind and matter, and as regards the number of substances. Descartes allowed three substances, God, mind and matter; Spinoza admitted God alone. For Descartes, extension is the essence of matter; for Spinoza, both extension and thought are attributes of God. Leibniz held that extension cannot be an attribute of a substance. His reason was that extension involves plurality, and can therefore only belong to an aggregate of substances. He believed, consequently, in an infinite number of substances, which he called “monads.”
Leibniz had a “principle of sufficient reason” according to which nothing happens without a reason; but when we are concerned with free agents, the reasons for their actions “incline without necessitating.” What a human being does always has a motive, but the sufficient reason of his action has no logical necessity.
Leibniz’s arguments for the existence of God are:
1. the ontological argument
2. the cosmoiogical argument
3. the argument from eternal truths
4. the argument from the pre-established harmony, which may be generalised into the argument from design, or the physicotheological argument, as Kant calls it.
Russell believes Leibniz abstained from publishing, because he kept on finding evidence that Aristotle’s doctrine of the syllogism was wrong on some points and respect for Aristotle made it impossible for him to believe this so he mistakenly supposed that the errors must be his own.
Unlike Spinoza, Leibniz didn’t challenge Aristotelian views.
In summary, Leibniz based his philosophy upon two logical premises: the law of contradiction and the law of sufficient reason. Both depend upon the notion of an “analytic” proposition, which is one in which the predicate is contained in the subject. The law of contradiction states that all analytic propositions are true. The law of sufficient reason (in the esoteric system only) states that all true propositions are analytic.
Russell believes Leibniz to be ‘a dull writer’, and his effect on German philosophy was to make it pedantic and arid unlike Descartes who was ‘un-pedantic’.