It can be very easy to generalize the beliefs and opinions of our founding fathers as the culture of the time seems much more simplified than now. Perhaps ironically, that generalization differs depending on who you ask. Some say they were all “Christian” as if that leaves no room whatsoever for variances in beliefs. Some say many or must were Deists in an attempt to separate them from religious belief. Some say that the colonies were intended for the religious freedom of Christians, as if it was only considered acceptable if the beliefs fell within that spectrum. Often we hear about the United States’ “Judeo-Christian heritage.” At this point you get the idea.
What I want to do here is show you the true spectrum of beliefs and acceptance of other belief systems during the Revolutionary War. Yes, many of our founding fathers were Christians but that doesn’t negate the wide array of beliefs and opinions they held. And for that matter, many colonists didn’t even welcome all Christians. Now people often think that different denominations and all doesn’t really matter but back then differences of opinion on theological issues could be a major point of contention. I think this is something that many people could use a reminder of.
If you know of any quotes that would make a good addition, feel free to suggest it in the comments below! (I’ll only use information where citations are available, so if you know that too I appreciate the help.)
I couldn’t resist making Paine my first post because he was an unusual character and yet his writing contributed so much to our American Revolution. Paine was scandalous for the time in many ways, daring to challenge conventional thought and unconcerned about whether he made people uncomfortable in the process. His pamphlet Common Sense was instrumental in convincing many colonists of their rights to and the necessity of secession from Great Britain.
His Beliefs: Paine was, to all intents and purposes, a deist though he had been accused by some of being an atheist. He believed in a supreme, heavenly being but refused to subscribe to any one religion. His Age of Reason goes into a great deal of detail on this. To describe himself, Paine wrote:
“I believe in one God, and no more; and I hope for happiness beyond this life.
I believe in the equality of man; and I believe that religious duties consist in doing justice, loving mercy, and endeavoring to make our fellow-creatures happy.
But, lest it should be supposed that I believe in many other things in addition to these, I shall, in the progress of this work, declare the things I do not believe, and my reasons for not believing them.
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.” 
He wrote of Deism by name as well, stating that:
“The only religion that has not been invented, and that has in it every evidence of divine originality, is pure and simple Deism. It must have been the first, and will probably be the last, that man believes.”
On Other Beliefs: Although Paine was content to simply believe in the existence of a creator and in doing right to those around us, he does express that others have “the same right to their belief as I have to mine.” That didn’t mean that those other beliefs were free from his criticism though.
He was especially critical of Christianity:
“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.”
Some additional quotes from Age of Reason:
“Each of those churches shows 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 accuses the other of unbelief; and, for my own part, I disbelieve them all.”
“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.”
“When the Church Mythologists established their system, they collected all the writings they could find, and managed them as they pleased. It is a matter altogether of uncertainty to us whether such of the writings as now appear under the name of the Old and New Testament are in the same state in which those collectors say they found them, or whether they added, altered, abridged, or dressed them up.
Be this as it may, they decided by vote which of the books out of the collection they had made should be the WORD OF GOD, and which should not. They rejected several; they voted others to be doubtful, such as the books called the Apocrypha; and those books which had a majority of votes, were voted to be the word of God. Had they voted otherwise, all the people, since calling themselves Christians, had believed otherwise — for the belief of the one comes from the vote of the other. Who the people were that did all this, we know nothing of; they called themselves by the general name of the Church, and this is all we know of the matter.”
“Some Christians pretend that Christianity was not established by the sword; but of what period of time do they speak? It was impossible that twelve men could begin with the sword; they had not the power; but no sooner were the professors of Christianity sufficiently powerful to employ the sword, than they did so, and the stake and fagot, too; and Mahomet could not do it sooner. By the same spirit that Peter cut off the ear of the high priest’s servant (if the story be true), he would have cut off his head, and the head of his master, had he been able. Besides this, Christianity grounds itself originally upon the Bible, and the Bible was established altogether by the sword, and that in the worst use of it — not to terrify, but to extirpate. The Jews made no converts; they butchered all. The Bible is the sire of the Testament, and both are called the word of God. The Christians read both books; the ministers preach from both books; and this thing called Christianity is made up of both. It is then false to say that Christianity was not established by the sword.
The only sect that has not persecuted are the Quakers; and the only reason that can be given for it is, that they are rather Deists than Christians. They do not believe much about Jesus Christ, and they call the scriptures a dead letter. Had they called them by a worse name, they had been nearer the truth.”
“Nothing that is here said can apply, even with the most distant disrespect, to the real character of Jesus Christ. He was a virtuous and an amiable man. The morality that he preached and practised was of the most benevolent kind; and though similar systems of morality had been preached by Confucius, and by some of the Greek philosophers, many years before; by the Quakers since; and by many good men in all ages, it has not been exceeded by any.”
Not as well known as some but Rush was a very interesting man. Born in Pennsylvania, he was a skilled physician, wrote the first American textbook on chemistry, served as surgeon-general of the Continental Army and was later a professor at the University of Pennsylvania. Unfortunately for his patients, Rush was an avid supporter of the practice of bleeding. 
His Beliefs: Rush was a Presbyterian and wholly supportive of the Christian religion, up to the belief that we should base our public education on the Christian faith and teachings.
On Other Beliefs: Despite Christianity being his first choice, Rush was not opposed to the followers of other religions. He wrote:
“Such is my veneration for every religion that reveals the attributes of the Deity, or a future state of rewards and punishments, that I had rather see the opinions of Confucius or Mahomed inculcated upon our youth, than see them grow up wholly devoid of a system of religious principles.”
Further, he said:
“It is foreign to my purpose to hint at the arguments which establish the truth of the Christian revelation. My only business is to declare, that all its doctrines and precepts are calculated to promote the happiness of society, and the safety and well being of civil government.”
 Paine, Thomas. Age of Reason. http://www.ushistory.org/paine/reason/singlehtml.htm
 The Selected Writings of Benjamin Rush. Edited by Dagobert D. Runes. New York: Philosophical Library, 1947. http://press-pubs.uchicago.edu/founders/documents/v1ch18s30.html