You have to know something already to learn something new - starting from nothing you can get... nowhere.
This has been confirmed in computer science; but was already known for animal behaviour. For animals to learn new material, they need to begin with inborn instincts.
A blank slate just stays a blank slate because interpretation must be constrained - an infinite universe has infinite interpretations: attention must be focused, interpretation of experience must be somewhat like a multiple choice exam.
One way of understanding how we know something is the idea of microcosm, which is related to the idea of the world being a nested hierarchy.
The idea (a metaphysical framework, not a scientific discovery) is that the world is constituted of similar wholes, the larger containing the smaller.
For example, the idea of an organism such as a human extends both upward and downward: human society is (or can be) like an organism and the cells of the body are also like an organism. Insofar as we understand the nature and workings of the human organism, then we are able significantly to understand human society (which contains many human organisms) and the cell (many of which are contained by the human organism).
This is an hierarchy because the larger contains and organises the smaller levels - and because although the smaller influences the larger, this principle of organisation is - overall - in the direction of larger organising smaller.
So, we come into the world equipped with knowledge of the world because we are a microcosm of the world.
Thus, we know about the world because we know about ourselves; we know about our relation to the world, because we know about the relations within ourselves.
In a sense, of course, this only moves the problem one step backwards - how do we have knowledge of ourselves and the relationships within us?
Yet, in practise, modern man does not have a problem with the idea of us knowing about ourselves, this seems natural to us - so, the metaphysical principle of microcosm does some explanatory work - it does not leave things unchanged.
But the metaphysical principle of nested hierarchies at each level of which the lower is a microcosm of that above it, is precisely one of the most powerful and traditional methods of reasoning about the transcendental realm, and of answering philosophical questions about man's place in the universe.
This can be seen in nearly all ancient systems of knowledge.
Yet modern man - supposedly - rejects this principle; and asserts that there is no similarity between different entities and not hierarchy of organisation but each entity and level may have fundamentally different properties.
As a metaphysical assumption this leads to self-refutation, because each item of asserted knowledge stands alone and with no relation to any other item of knowledge - such that instead of the traditional nested hierarchy of similar entities that is traditional knowledge, the totality of knowledge is merely a disordered heap of unrelated factoids - and, even worse, none of these factoids have any validity since there is no reason to assume that a human could validly know anything about anything.
So, modern thought is incoherent and the attempt to live by it leads to nihilism.
There is no rational alternative but to return to the much derided idea of nested hierarchy as the basis of understanding.
And no difficulty about it either - since that is exactly how humans do interpret the world - spontaneously and without teaching: human anthropomorphise the world, that is humans naturally see the world as instances of humanity writ large or in microcosm, and their relations with the world as relations within such an hierarchy.
It all makes sense - so why was it rejected in favour of nihilistic incoherence?
Well, this is a good candidate for theological explanation - for an explanation in terms of the power of the Holy Spirit, and the power of that which opposed the Holy Spirit, in human history.