A more “practical” question could hardly be conceived. The preacher says: “Believe on the Lord Jesus Christ, and thou shall be saved.” But how can a man possibly act on that suggestion, unless he knows what it is to believe. It was at that point that the “doctrinal” preaching of a former generation was far more practical than the “practical” preaching of the present day. I shall never forget the pastor of the church in which I grew up. He was a good preacher in many ways, but his most marked characteristic was the plainness and definiteness with which he told the people what a man should do to be saved. The preachers of the present time allude to the importance of becoming a Christian, but they seldom seem to make the matter the subject of express exposition; they leave the people with a vague impression to the effect that being a Christian is a good thing, but this impression is difficult to translate into action because definite directions are absent. These preachers speak about faith, but they do not tell what faith is.
It is to help in some small way to supply this lack that the present little book (called What is Faith?) has been written. If the way of salvation is faith, it does seem to be highly important to tell people who want to be saved just what faith means. If a preacher cannot do that, he can hardly be a true evangelist.
In seven brief chapters, Machen goes on to give a solid, biblical answer to the important question; here are the chapter titles: Faith in God, Faith in Christ, Faith Born of Need, Faith and the Gospel, Faith and Salvation, Faith and Works, and finally, Faith and Hope. If you’ve not read this book, I very much recommend it. What is Faith? is not too long or difficult, and it is full of gospel truth and comfort. For those of you who need a hand to lead you again to Jesus, this book will do that.
The above quote is found in the introduction of Machen’s, What is Faith?