jmt356
The revelation given to man in (Rom. 1:19-20) is the first and most basic revelation to fallen man. It involves the work of creation by God. It involves the stamp of God upon every man, that he can know of God. (1:19) The creation preaches the Gospel. You have a creation, there must be a Creator. This was, is, sufficient revelation to render man responsible in his decision to want or reject God.
And, it will not just be the fact of creation itself, but God wrote the Gospel in the heavens, in the stars. (Ps. 19:1-6) We know it as the Zodiac today. See (Job 38:32)
When God reveals, His revelation is to be preached. It provides man access to God, and to know something of God. Thus we are told in (Gal. 3:8) that the gospel was preached to Abraham when God said to him, "In thee shall all nations be blessed".
So, as God continues to add to His revelation to man, it is to be made known. That basic revelation becomes quite involved being fleshed out in experience on earth. It involves a distinct nation of God, Israel. It will involve a distinct Person of God, Jesus Christ. It will involve the Gentiles when the nation of Israel turns away from God. This will all be fully presented in Paul's gospel. (Gal. 1:11-12) And should be preached.
So, in every age the Gospel is preached, whether it be in it's most basic form or whether it be in it's complete form that we have today and are still learning of. And in every age, man is accountable to it.
The 'hearing' aspect of the Gospel centers on those who are receiving the Gospel. It doesn't always speak to hear with just the ears. It can be getting understanding through the creation or the written Word of God. When we are told to hear in the Scripture, we are being told to respond correctly to what is being said.
In (Rom. 10) Paul is addressing Israel. They rejected Christ and they reject the present gospel of Christ. In so doing, Israel didn't just reject the gospel of Christ, she rejected all the revelation that had been given up to that time from God. (Rom. 10:16-21). And Paul specifically alludes to (Ps. 19:1-6), the most basic revelation given in the stars. (Rom. 10:18)
So, the basic answer to your question is, no one can know anything about God unless He reveals it. As He reveals it, and adds to it, to whom He reveals it, we are required to make it known.
Quantrill