Thomas Paine in "The Age of Reason"

Revelations or Human Inventions?

 "I do not believe in the creed professed by the Jewish church, by the Roman church, by the Greek church, by the Turkish church, by the Protestant church, nor by any church that I know of. My own mind is my own church.  All national institutions of churches, whether Jewish, Christian or Turkish, appear to me no other than human inventions, set up to terrify and enslave mankind, and monopolize power and profit. "

Which Revelations to Believe?

Every national church or religion has established itself by pretending some special mission from God, communicated to certain individuals. The Jews have their Moses; the Christians their Jesus Christ, their apostles and saints; and the Turks their Mahomet, as if the way to God was not open to every man alike.

Each of those churches show certain books, which they call revelation, or the word of God. The Jews say, that their word of God was given by God to Moses, face to face; the Christians say, that their word of God came by divine inspiration: and the Turks say, that their word of God (the Koran) was brought by an angel from Heaven. Each of those churches accuse the other of unbelief; and for my own part, I disbelieve them all. 

Your Revelation Becomes Hearsay for Others

"No one will deny or dispute the power of the Almighty to make such a communication if he pleases. But admitting, for the sake of a case, that something has been revealed to a certain person, and not revealed to any other person, it is revelation to that person only. When he tells it to a second person, a second to a third, a third to a fourth, and so on, it ceases to be a revelation to all those persons. It is revelation to the first person only, and hearsay to every other, and, consequently, they are not obliged to believe it.

It is a contradiction in terms and ideas to call anything a revelation that comes to us at second hand, either verbally or in writing. Revelation is necessarily limited to the first communication. After this, it is only an account of something which that person says was a revelation made to him; and though he may find himself obliged to believe it, it cannot be incumbent on me to believe it in the same manner, for it was not a revelation made to me, and I have only his word for it that it was made to him."

On Morality and Ten Commandments:

When Moses told the children of Israel that he received the two tables of the commandments from the hands of God, they were not obliged to believe him, because they had no other authority for it than his telling them so; and I have no other authority for it than some historian telling  me so. The commandments carry no internal evidence of divinity with them; they contain some good moral precepts, such as any man qualified to be a lawgiver, or a legislator, could produce himself, without having recourse to supernatural intervention.  It is, however, necessary to except the declaration which says that God visits the sins of the fathers upon the children; it is contrary to every principle of moral justice. 

On Christianity an an Organized Religion

Of all the systems of religion that ever were invented, there is none more derogatory to the Almighty, more unedifying to man, more repugnant to reason, and more contradictory in itself, than this thing called Christianity. Too absurd for belief, too impossible to convince, and too inconsistent for practice, it renders the heart torpid, or produces only atheists and fanatics. As an engine of power it serves the purpose of despotism; and as a means of wealth, the avarice of priests; but so far as respects the good of man in general, it leads to nothing here or hereafter.

On Christian Theology
The study of theology, as it stands in Christian churches, is the study of nothing; it is founded on nothing; it rests on no principles; it proceeds by no authorities; it has no data; it can demonstrate nothing; and it admits of no conclusion. Not any thing can be studied as a science, without our being in possession of the principles upon which it is founded; and as this is not the case with Christian theology, it is therefore the study of nothing.