In Ayn Rand's, Anthem, it is said that the secrets of the earth are not for all men to see. It is a statement of entitlement. Those who do the work and pursue the secrets of the earth are therefore entitled to get the knowledge that ensues. It is up to them whether they chase it or not. So, Prometheus (and Rand) is stating that those who go after knowledge do eventually get to see the secrets of the earth, while otheres that don't, aren't entitled to know it.
