For part I, see here. The original pamphlet is here. This is Charles Chauncy's argument for universal salvation. Chauncy believed both reason and revelation proved universal salvation and that the Trinity was false. He was a founding era Christian-unitarian universalist. He was also a key influence on the American Founding. Chauncy's "Christianity" not Jonathan Edwards' arguably was the political-theological motivator behind the Declaration of Independence and Constitution.
On with Part II:
These supposed doctrines of revelation have so long been received for important truths, not by the vulgar only, but by persons venerable for their learning and piety, whose business it has been to enquire into things of this nature, that it may seem to many an affection of novelty, if not an argument of something worse, so much as to call them in question. Multitudes, having been taught, from their early childhood, the doctrine of eternal torments, and, what is commonly connected with it, the final, misery of the greatest part of mankind, are become insensibly and strangely prepossessed in favor of these tenets, however shocking to unprejudiced minds; insomuch that it would be no wonder, if they should determine, at once, without examination, that an essay intended to prove, that the scheme of redemption concerns the human race universally, and will, in its final result, inflate them all, without distinction or limitation, in perfect blessedness, must needs be an heretical undertaking, the very proposal of which ought to be rejected, as carrying along with it its own confutation.
But yet, there are some, it may be hoped, who are not so far under the government of prejudice, but that they can suspend their censures, at lead, till they have deliberately read what may be offered from the books themselves, containing the revelations of God, in support of the hypothesis, that all men shall finally be happy. And should it be found capable of being fully confirmed by solid proofs, from these books, none who regard their authority, as sacred, should withhold their assent. To be sure, they ought not to do so, as being influenced thereto by an undue attachment to their spiritual leaders, however renowned for knowledge, or judgment, or exemplary virtue: For they are certainly fallible, and may therefore be mistaken.
And this, I am deeply sensible, is the truth with respect to myself. I know I am liable to err, in common with other men. Nay, I pretend not but I may have been betrayed, in the present case, into an apprehension of that as true, which is really false through the undue prevalence of some undiscerned wrong bias or other. For which reason, instead of finding fault with any, into whose hands these papers may fall, for reading them with caution, I would seriously advise them to do so lest they should be deceived with the mere appearance appearance of truth: Only, they ought so take care that they do not so mix prejudice and jealousy with their caution, as to prevent a fair and impartial enquiry. All I desire is, that, if the proofs here offered should appear to any, upon a thorough examination, to be justly conclusive, they would honestly yield to conviction. If they should perceive no strength in them, or not strength sufficient to support the cause that is rested on them, I think, they would act commendably, and becoming their character as men and Christians, if they should still adhere to their former sentiments. Every man must judge for himself: though, if his judgment is wisely and reasonably formed, it will be the effect of apparent evidence, upon an honest and full enquiry.
That I may proceed, in the illustration of this subject, without perplexity, I shall begin with mentioning a few things, in a preliminary way, tending to prevent a misconception of my meaning, when I affirm, that all men shall be finally happy. It will then be natural to exhibit the proper arguments in support of this affirmation: Which, having confirmed by direct proofs, I shall endeavour further to strengthen by particularly going over, and invalidating the contrary evidence. [Italics in original.]