The moral courage and the personal integrity that exemplified his entire life marks his written work. Age of Reason was a book that caused such an explosion in its time that it did two things - immortalized him for posterity and condemned him during his lifetime. 

When he is attacking Christianity, he maintains his good quality acerbic humour to mock the beliefs and at the same time gives irrefutable proof of why he considers the beliefs to be wrong. He picks up different aspects of Christianity - the bible and its different books, the characters of Moses, Joshua, Jesus and the significant events on which Christianity is based - most importantly the resurrection of Jesus. This was written to make perfect sense to a complete layman on the street. And this it does brilliantly!!!

“You will do me the justice to remember, that I have always strenuously supported the Right of every Man to his own opinion, however different that opinion might be to mine. He who denies to another this right, makes a slave of himself to his present opinion, because he precludes himself the right of changing it.”

“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”

“My own mind is my own church.”

“But it is necessary to the happiness of man, that he be mentally faithful to himself”

“Infidelity does not consist in believing, or in disbelieving; it consists in professing to believe what he does not believe.”

“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”

“The more unnatural anything is, the more it is capable of becoming the object of dismal admiration.”

“THE WORD OF GOD IS THE CREATION WE BEHOLD and it is in this word, which no human invention can counterfeit or alter, that God speaketh universally to man”

“and, therefore, the only idea we can have of serving God, is that of contributing to the happiness of the living creation that God has made. This cannot be done by retiring ourselves from the society of the world and spending a recluse life in selfish devotion.”

“As mystery answered all general purposes, miracle followed as an occasional auxiliary. The former served to bewilder the mind, the latter to puzzle the senses. The one was the lingo, the other the legerdemain. And, in the second place, it is degrading the Almighty into the character of a showman, playing tricks to amuse and make the people stare and wonder.”

“Upon the whole, mystery, miracle, and prophecy are appendages that belong to fabulous and not to true religion. They are the means by which so many Lo, heres! and Lo, theres! have been spread about the world, and religion been made into a trade”

“It is certain that, in one point, all the nations of the earth and all religions agree—all believe in a God; the things in which they disagree, are the redundancies annexed to that belief; and, therefore, if ever a universal religion should prevail, it will not be by believing anything new, but in getting rid of redundancies”

“Speaking for myself, if I had no other evidence that the Bible is fabulous than the sacrifice I must make to believe it to be true, that alone would be sufficient to determine my choice”

“Divided love is never happy.for it is impossible to derive happiness from the company of those whom we deprive of happiness.”

“To be happy in old age, it is necessary that we accustom ourselves to objects that can accompany the mind all the way through life, and that we take the rest as good in their day. The mere man of pleasure is miserable in old age, and the mere drudge in business is but little better; whereas, natural philosophy, mathematical and mechanical science, are a continual source of tranquil pleasure, and in spite of the gloomy dogmas of priests and of superstition, the study of these things is the true theology; it teaches man to know and to admire the Creator, for the principles of science are in the creation, and are unchangeable and of divine origin”

“for when we cease to have an object, we become like an invalid in a hospital waiting for death”

“Can we suppose it is consistent with the wisdom of the Almighty, to commit himself and his will to man upon such precarious means as these, or that it is consistent we should pin our faith upon such uncertainties? We cannot make, nor alter, nor even imitate so much as one blade of grass that he has made, and yet we can make or alter words of God as easily as words of man

“But all other arguments apart, the consciousness of existence is the only conceivable idea we can have of another life, and the continuance of that consciousness is immortality. The consciousness of existence, or the knowing that we exist, is not necessarily confined to the same form, nor to the same matter, even in this life”

“credulity, however, is not a crime, but it becomes criminal by resisting conviction.”

“but when it is said, as in the Testament, “If a man smite thee on the right cheek, turn to him the other also;” it is assassinating the dignity of forbearance, and sinking man into a spaniel.Those who preach this doctrine of loving their enemies are in general the greatest persecutors, and they act consistently by so doing”

“And is not the evidence that this creation holds out to our senses infinitely stronger than anything we can read in a book that any impostor might make and call the word of God? As for morality, the knowledge of it exists in every man’s conscience”

“Religion, by such means, becomes a thing of form, instead of fact—of notion, instead of principles; morality is banished to make room for an imaginary thing called faith”

“certain as I am, that when opinions are free, either in matters of government or religion, truth will finally and powerfully prevail.”