The first act of faith.

Herman Witsius has written:

“The fist thing which faith either comprehends or presupposes, is the knowledge of the thing to be believed. This appears in opposition to Popish triflers, I. From express passages of scripture, which so speak concerning faith as manifestly to intimate, that knowledge is included in its very notion and exercise, Isa. liii. 11. John xvii. 3. compared with Heb. ii. 4. John vi. 69. 2 Tim. i. 3. II. From the nature of faith itself, which, as it doubtless means an assent given to a truth revealed by God, necessarily presupposes the knowledge of these tow things. (1.) That God has revealed something. (2.) What that is to which assent is given, as a thing divinely revealed. For it is absurd to say, that a person assents to any truth which he is entirely ignorant of, and concerning which he knows of no testimony extant worthy of credit. III. From the manner in which faith is produce in the elect; which is done externally by preaching and hearing of the Gospel, Rom. x. 27. revealing that which ought to be believed, with the demonstration of the truth to every man’s conscience, 2 Cor. iv. 2. and internally by the teaching of God the Father, John vi. 45. If therefore faith be generated in the heart by a teaching both external and internal, it must of necessity consist in knowledge: for knowledge is the proper and immediate effect of such instruction. IV. From the consequence annexed, which is confession and apologia [greek], or giving an answer, Rom. x. 9, 10. 1 Pet. iii. 15. But it is impossible, that this should be with knowledge. Hilary said well, “For none can speak what he knows not; nor believe what he cannot speak.” ...

“Moreover those things which are necessary to be known by the person who would believe, are in general, the divinity of the scriptures, into which faith must be ultimately resolved; more especially, those things which regard the obtaining of salvation in Christ; which may summarily be reduced to these three heads: 1st. To know, that by sin thou art estranged from the life of God, and art come short of the glory of God, Rom. iii. 23. That it is not possible, that either thou thyself, or an angel from heaven, or any creature in the world, nay, or all the creatures in the universe, can extricate thee from the abyss of misery, and restore thee to a state of happiness. 2dly. That thou shouldst know Christ this Lord to be full of grace and truth, John i. 14. who is that only name given under heaven, whereby we can be save, Acts. iv. 1. and in the knowledge of whom consists eternal life, John xvii. 3. 3dly. That thou shouldst know, that, in order to thy obtaining salvation in Christ, it is necessary that thou be united to Christ, by the Spirit and by faith, and give up thyself to him, not only be justified, but also sanctified, and governed by his will and pleasure, proving what is that good, and acceptable, and perfect will of God, Rom. xii. 2.”

Witsius, Herman. The Economy of the Covenants Between God and Man, Volume I, Kingsburg, CA: den Dulk Christian Foundation, 1990, p. 375-377)