Innate or learned?
On the axis: Source of knowledge · an innate idea
Are we born with an empty mind, a blank page the senses fill in, or do we already possess, before any experience, ideas or structures that experience merely awakens?
This problem is brought out by the thought experiment Molyneux's problem:
Imagine a man blind from birth who has learned to tell a cube from a sphere by touch: hands on them, he can say which is which. One day, through an operation, he gains his sight. The cube and the sphere are set before him, without his being able to touch them. Will he be able, by sight alone, to say which is the cube and which the sphere?
Molyneux, reported in Locke's Essay (1688)
Will he recognize the shapes by sight alone, or is everything to be learned from the senses?
Your choice above is recorded in your profile. See my profile →
Justification
If an idea were truly , it would be universally acknowledged; yet neither "whatever is, is" nor any moral principle is so to children, idiots or distant peoples. Locke thus turns the Cartesian argument from universal consent against and the rationalist school: the mind at birth is a , and every idea can be traced back to sensation (external objects) or reflection (the mind's operations on its own ideas). The wager is bold: to show that these two sources alone suffice to compose the whole content of thought, down to the most abstract notions.
Let us suppose the mind to be, as we say, white paper, void of all characters, without any ideas: how comes it to be furnished? ... To this I answer, in one word, from experience.Essay Concerning Human Understanding, II, ch. 1, §2
Essay Concerning Human Understanding, I (against innate ideas) and II, ch. 1 (sensation and reflection)
Justification
Against the empiricism of Locke, for whom nothing is in the understanding that was not first in the senses, Leibniz replies: nothing, except the understanding itself. The mind is not a but carries within it in potency, like veins in marble; necessary truths (logic, mathematics, metaphysics) cannot come from experience, which yields only particular cases. This is an avowed , tempered by acknowledging the role of the senses for truths of fact.
Nothing is in the intellect that was not first in the senses, except the intellect itself.New Essays on Human Understanding, II, 1
New Essays on Human Understanding, preface and book II, ch. 1 · New Essays, II, 1, §2 (the veins in the marble)