"The doctrine of the Gospel is not only true, to work upon the understanding, but it is good, so as to move and draw the will:
"It is a trustworthy statement, deserving full acceptance, that Christ Jesus came into the world to save sinners, among whom I am foremost of all." (1 Timothy 1:15, NASB)
It is an excellent doctrine to ravish the will. Now, observe what a great deal of difference there is between men in believing...
Some that hear the Gospel, and have only a literal knowledge of it, so as to be able to talk of it, so as to understand the words and syllables, to know what it means; they may have some clearness of understanding this way, but there is not a sound assent.
There are others affected so with the Gospel, as by the common influence of the Spirit they may assent to the truths delivered concerning God and Christ, and salvation by him, yet do not give it entertainment in their hearts. These may be said to seek God, but not with the whole heart. A speculative, naked, and cold assent they may have, but that is not enough. It is not enough to see food that is wholesome, but you must eat it. Nor is it enough to understand the Gospel, and believe that it is true, but we must embrace it; it must be accepted, else we do not believe with the whole heart. The word is propounded to man as true. Now, the truth made known may cause a speculative assent. This may draw profession after it; and this we call historical faith, because we are no more affected with the Gospel than with an ordinary history which we read and believe. The word is propounded again as good, to move and excite the will.
Now, there is a twofold good—the good of happiness, and the good of holiness. The good of happiness, that which is profitable and sweet. Then there is the good of holiness. Now, there are many that look upon the Gospel as good and profitable, because it offereth pardon and eternal life; such comfort to the conscience, and such good to our whole souls. We may be affected with it as a good doctrine. Naturally, man hath not only a sense of religion, but he hath a hunger after immortality and everlasting blessedness. Therefore, since the Gospel doth so clearly promote happiness, it may be greedily catched hold of by those whose hearts are affected, while they look upon it under these notions; and they may be so far affected that they may for a while not only profess it out of danger, but when some danger doth arise they may defend their opinions with some care. Yet this is not with all the heart. Why? As soon as any great danger doth arise, out of which there is no escape... as soon as persecution arose, saith Christ, all this ardour and heat of spirit which they did formerly seem to have, comes to nothing. What is the reason it vanisheth? Because they receive the Gospel rather upon those notions of interest and profit, than of duty and holiness; and the impression of the profitableness of the Gospel, as a doctrine of happiness, was not so deeply rooted in them, not so durable, that the hope of the future good would be prevalent over the fear of present evil and danger.
There may be some desires of heaven in a carnal breast, but they are easily blotted out by worldly temptations; but the true desires of holiness are lasting, and will prevail over our lusts."
(Thomas Manton, 1620-1677)
(Thomas Manton's Exposition of Psalm 119:10)