Now, since Christ cannot be seen with our eyes, nor touched with our hands, while he is in heaven and we are on earth, and that he is not known to us but by his word of the gospel, what other way can we unite with him, but believing on this unseen Christ? So that faith is the only mean on our part. And its fitness for this work appears, if ye consider,
(1.) That faith is a self-emptying and creature-emptying grace, throwing off and putting away all those things that might keep the soul at a distance from Christ, Phil. 3:8.
And, (2.) It is as much fitted to receive an unseen Christ and salvation, which appears to us only in the word, as the hand to receive what can he received into it. For in the word Christ offers himself and all his salvation to us, which we cannot lay hold of by any bodily action whatsoever; but faith crediting the testimony, consenting to, and resting on the offered Christ, with his salvation, does actually get the same, as sure as there is truth in the word of the gospel.
The Whole Works of Thomas Boston: An Illustration of the Doctrines of the Christian Religion, Part 1, ed. Samuel M‘Millan, vol. 1 (Aberdeen: George and Robert King, 1848), 547-548.