Romans 1:19

That which may be known [τ ο γ ν ω σ τ ο ν]. So A. V. and Rev., as equivalent to that which is knowable. But that which is knowable was not revealed to the heathen. If it was, what need of a revelation? Better, that which is known, the universal sense in the New Testament, signifying the universal objective knowledge of God as the Creator, which is, more or less, in all men.

In them. In their heart and conscience. The emphasis should be on in. Thus the apparent tautology - what is known is manifest - disappears.