Clarity, in my view, starts out by distinguishing what we really know and what are just speculations. However, due to our very limited power of understanding, it is easy for us to go about speaking as if we really do understand what we are talking about (yes, this applies to me too).
When we realize that we might be simply be a copy-cat of some enduring ways of seeing the world in our society we might gather the curiosity to check: what part of this immense "knowledge" is actually true, of what part can I be certain using my own powers of thought?
Well, this is the answer that Descartes posed himself. His answer was that the only thing I could be absolutely sure about was my own existence. This is because even the things I see the most clearly and distinctly may be illusions planted on my mind (I could be in a simulation run by some evil programmer). To Descartes the only way to leave this pit of absolute ignorance was to trust that all things that we conceive clearly must be true. But how coudl we do that? It seems obvious to me that a square has four sides, but couldn't this clear evidence be the product of an illusion, a simulation, an evil dream? the problem arises because we are questioning the powers of the mind, but we only have the mind to assess its own powers. So if we start by doubting we get lost, apparently nothing can help us.
Descartes would probably have died a convicted skeptic were it not for his assertion that one could know the existence of God with the same degree of certainty as one know one's own. He said it was necessary just to examine the idea of God to see how certain it implied God's existence. But this argument has, understandably, garnered few followers.
What I am attempting to say is that, individually, we are very weak. Individually we are perhaps not more clever than the average seal, bear or gorilla. But, immersed in a society we gather a culture, we learn how to speak, how to think, how to interpret the world with concepts that no single man would have been able to devise. Me, you, we are in large part the living remains of our ancestors. Although their physical bodies are dead, their minds, their theories, the way they reacted to the world, their ways of being are selectively reenacted in each of us. We are reincarnations of them, not just of their ideas, but their way of feeling, of seeing, of reacting. If this is the sense given to "meme", then indeed we have learned to reproduce in terms of memes and not only of genes.