The truth of Christianity must be handled with care, particularly in sharing it with others. We are called to be witnesses as J. Gresham Machen explains below:
The character of Christianity as founded upon a message is summed up in the words of the eighth verse of the first chapter of Acts — ’Ye shall be my witnesses both in Jerusalem, and in all Judea and Samaria, and unto the uttermost part of the earth.’ It is entirely unnecessary, for the present purpose, to argue about the historical value of the Book of Acts or to discuss the question whether Jesus really spoke the words just quoted. In any case the verse must be recognized as an adequate summary of what is known about primitive Christianity. From the beginning Christianity was a campaign of witnessing. And the witnessing did not concern merely what Jesus was doing within the recesses of the individual life. To take the words of Acts in that way is to do violence to the context and to all the evidence. On the contrary, the Epistles of Paul and all the sources make it abundantly plain that the testimony was primarily not to inner spiritual facts but to what Jesus had done once and for all in His death and resurrection.
Christianity is based, then, upon an account of something that happened, and the Christian worker is primarily a witness. But if so, it is rather important that the Christian worker should tell the truth. When a man takes his seat upon the witness stand, it makes little difference what the cut of his coat is, or whether his sentences are nicely turned. The important thing is that he tell the truth, the whole truth, and nothing but the truth. If we are to be truly Christians, then, it does make a vast difference what our teachings are, and it is by no means aside from the point to set forth the teachings of Christianity in contrast with the teachings of the chief modern rival of Christianity.
The chief modern rival of Christianity is ‘liberalism.’ An examination of the teachings of liberalism in comparison with those of Christianity will show that at every point the two movements are in direct opposition. (Christianity and Liberalism)