From Peter Forsyth, The Work Of Christ; Cf. The Work of Christ at Amazon

In the days of our fathers Christian belief was more solid within the Church than it is now; and the defending and expounding of Christianity, more especially the defending of it, had to concern itself with outsiders – outside the Church, and outside Christianity very often. Today our difficulties have changed; and a great part of our exposition must keep in view the fact that some of the most dangerous challenges of Christianity are found amongst those who claim the Christian name. There are those who have a very real reverence for the character of Jesus Christ, and they can speak, and do speak, quite sincerely, with great devotion and warmth and beauty, about Christ, and about many of the ideas that are associated with apostolic Christianity. All the same, they are strongly and sometimes even violently, antagonistic to that redemption which is the very center of the Christian faith; and they make denials and challenges which are bound to tell upon the existence of that faith before many generations are over. We do not take the true measure of the situation unless we realize that the thing which is at stake at this moment is something that will not affect the present generation, but is sure to affect two or three generations hence. Those who are concerned about Christianity on the largest scale today are concerned with what may be its position and its prospects then. The ideas at the center of the Christian faith are too large, too deep and subtle, to show their effects in one age; and the challenge of them does not show its effect in one generation or even in two. Individuals, society, and the Church, indeed, are able to go on, externally almost unaffected, by the way that they have upon them from the past; and it is only within the range of several generations that the destruction of truths with such a comprehensive range as those of Christianity takes effect. Therefore it is part of the duty of the Church, in certain sections and on certain occasions, to be less concerned about the effect of the Gospel upon the individual immediately, or on the present age, and to look ahead to what may be the result of certain changes in the future. God sets watchmen in Zion who have to keep their eye on the horizon; and it is only a drunken army that could scout their warning. We are not only bound to attend to the needs and interests of the present generation; we are trustees for a long future, as well as a long past. Therefore it is quite necessary that the Church should give very particular attention to these central and fundamental points whose influence, perhaps, is not so promptly prized, and whose destruction would not be so mightily felt at once, but would certainly become apparent in the days and decades ahead.