As any who have read his Father Brown stories know, Gilbert Keith Chesterton (1874-1936) was a man of uncommon good sense. His book Orthodoxy is much read, and deservedly so. This quotation concerning the idea that 'all religions are really the same in essence' is a gem, and so I make no apologies for bringing it before the world:
"The things said most confidently by advanced persons to crowded audiences are generally those quite opposite to the fact; it is actually our truisms that are untrue. Here is a case. There is a phrase of facile liberality uttered again and again at ethical societies and parliaments of religion: "the religions of the earth differ in rites and forms, but they are the same in what they teach." It is false; it is the opposite of the fact. The religions of the earth do not greatly differ in rites and forms; they do greatly differ in what they teach. It is as if a man were to say, "Do not be misled by the fact that the Church Times and the Freethinker look utterly different, that one is painted on vellum and the other carved on marble, that one is triangular and the other hectagonal; read them and you will see that they say the same thing." The truth is, of course, that they are alike in everything except in the fact that they don't say the same thing. An atheist stockbroker in Surbiton looks exactly like a Swedenborgian stockbroker in Wimbledon. You may walk round and round them and subject them to the most personal and offensive study without seeing anything Swedenborgian in the hat or anything particularly godless in the umbrella. It is exactly in their souls that they are divided. So the truth is that the difficulty of all the creeds of the earth is not as alleged in this cheap maxim: that they agree in meaning, but differ in machinery. It is exactly the opposite. They agree in machinery; almost every great religion on earth works with the same external methods, with priests, scriptures, altars, sworn brotherhoods, special feasts. They agree in the mode of teaching; what they differ about is the thing to be taught. Pagan optimists and Eastern pessimists would both have temples, just as Liberals and Tories would both have newspapers. Creeds that exist to destroy each other both have scriptures, just as armies that exist to destroy each other both have guns." G. K. Chesterton, Orthodoxy, Pp. 333-4 of The Collected Works of G. K. Chesterton, Vol. 1 (Ignatius Press, San Francisco, 1986)
The Church Times is an Anglican paper, and the Freethinker a sceptical journal. Surbiton and Wimbledon are London suburbs where one might reasonably be expected to find a stockbroker, at least in 1908 when Chesterton was writing.