Gottfried Wilhelm Leibniz
We live in the best of all possible worlds.
Gottfried Wilhelm Leibniz (1646 – 1716, Germany) : rationalism. Nothing happens without a reason: this is the principle of sufficient reason. Leibniz takes it all the way. On AskPhilosophy: 6 reconstructed arguments, 4 quotes checked word for word against the original texts, and 3 common beliefs examined; every text carries an authenticity badge (written by the author, posthumous, student notes, reported, apocryphal).
Why he matters
He invented the infinitesimal calculus at the same time as Newton, independently: our notations dx and ∫ come from him. He studied binary arithmetic and built a calculating machine. In philosophy, his question "why something rather than nothing?" and his principle of sufficient reason remain central to debates about God.
His times
A lawyer, diplomat, librarian and historian in the service of the dukes of Hanover, he wrote thousands of letters to scholars all over Europe. In Paris (1672-1676) he met Huygens, Arnauld and Malebranche; he visited Spinoza in 1676. In his lifetime he published only one book of philosophy, the Theodicy (1710), and he died almost forgotten.
His positions
click a row to see the evidenceGod is the ultimate reason of things: a necessary substance, perfect in power, wisdom and goodness. He proves it in several ways, from the contingency of the world as well as from the mere idea of a necessary being.
Against Locke, he defends innate ideas: the mind is not a blank tablet but veined marble, in which truths are inscribed as dispositions. Necessary truths come from the mind, even though we would never think of them without the senses.
Truths of reasoning (mathematics, logic) are necessary and can be demonstrated down to self-evident principles. Truths of fact also have a reason, even if we rarely know it fully.
Perception cannot be explained by moving parts: it belongs to simple substances. This is not Descartes' dualism: for Leibniz everything real is made of such perceiving units, and soul and body agree through a "pre-established harmony", without acting on each other.
Everything has a reason, so everything is determined in advance, but nothing is necessary in the logical sense: reasons "incline without necessitating". Being free means acting with understanding, from oneself, while the opposite remains possible. A compatibilist for most readers.
Goodness does not depend on God's mere will: if will took the place of reason, justice would be the justice of tyrants. The rules of goodness lie in the nature of things.
Faith and reason agree: a mystery may be above reason (we cannot comprehend it), never against it (it contradicts no certain truth).
The world is ordered to the best, and happiness is not rest: it is endless progress towards new pleasures and new perfections.
Creatures are limited by nature, but minds can progress endlessly in knowledge and perfection.
He wrote a great deal on law, peace in Europe and the reunion of the Churches; these texts are not yet in our corpus.
An ethics of love and perfection: to love is to take pleasure in another's happiness; the wise person tends towards every good and does the best possible.