Gottfried Wilhelm Leibniz
(1646 – 1716)
German philosopher, mathematician, scientist and diplomat. He is known as the last universal genius. He made major contributions to physics and technology and anticipated many notions that surfaced later in computer sciences, geology, biology, medicine and probability theory. He is considered one of the greatest representatives of 17th century Rationalism (together with Descartes and Spinoza).
In philosophy, he is most famous and noted for his optimism – the idea, that our world is the best possible world that God could have created. He proposed a complex system built on the foundations of Descartes. The main buildings blocks of his system can be summarized in three main principles:
(1) principle of Identity & principle of non-contradiction : propositions are divided into two types:
– necessary (later called analytic) propositions are (1) true by definition, (2) necessary (cannot be false), (3) a priori (known independently of observation)
– for example: the sentence “All bachelors are men” – must be true by definition, it cannot be that “All bachelors are not men”, in the same way that “2+3=5” and it cannot be that “2+3≠5”
– contingent (later called synthetic) propositions are (1) not true by definition (their truth or falsity depends on the facts of the world), (2) contingent (they could be false if facts are different), (3) a posteriori (their truth or falsity is known by observation)
– for example: the sentence “The cat is on the carpet” is not true by definition, it would be false if the cat was not lying on the carpet, or if there was a dog lying there instead. In order to determine if the sentence is true, we have to look at the carpet and see if the cat is really there.
* Further, Leibniz made the important claim that sub specie aeternitatis (from God’s point of view), all synthetic sentences are actually analytic (see below)
(2) principle of sufficient reason: for anything that exists, there is a reason why it exists and why it exists exactly in the way it does – nothing happens without a reason
(3) principle of internal harmony: God must be both rational and good, and must desire and be capable of creating the maximum amount of existence possible (metaphysical perfection) and the maximum amount of activity (moral perfection).
—> At the moment of creation of the world, God entertained all possibilities, but actualised only those that would guarantee the maximum metaphysical and moral perfection. So, God has created the world and all entities in it in a way that they necessarily harmonize with each other to the greatest extent possible.
—> * The above principles also explain his claim why all synthetic propositions are actually analytic – even though a proposition might seem contingent, it is in fact that it must be so. When “the cat is on the carpet”, it had to be that it is there.
The above principles also propose a solution to the mind-body problem. In one of his best known metaphors, Leibniz imagines that the mind and the body are like two pendula clocks, moving in perfect harmony. In order to always be moving in synchronicity, there either has to be (1) a causal link/physical connection between them that ensures it (like the Cartesian pineal gland), (2) someone whose only job is to constantly synchronise the clocks, or (3) to design and construct the clock so perfectly that they will always remain synchronised with each other, without the need to have a causal link or someone making adjustments.
—> Leibniz thought that option (c) is the superior one, and that God, with his infinite wisdom and foreknowledge, established the mutual correspondence and harmony of the two clocks.
Leibniz also proposed that the universe is made of an infinite number of simples substances known as monads (described in Monadologie, 1714). They are kind of psychic forces, that have no parts and exist as qualities. They are the simplest and realest ‘things’ that can exist independently of one another. Each monad is entirely unique and contains all its future states and is continuously changing over time. Monads are centers of force, while space, matter and motion are phenomenal and relative. The idea went against Newton’s theory and anticipated Albert Einstein’s theory of relativity.