The remainder of the psalm holds fast by that thought of the great deeds of God in the past. It is a signal example of how the same facts remembered may depress or gladden, according to the point of view from which they are regarded. We can elect whether memory shall nourish despondency or gladness. Yet the alternative is not altogether a matter of choice; for the only people to whom "remembering happier things" need not be "a sorrow's crown of sorrow" are those who see God in the past, and so are sure that every joy that was and is not shall yet again be, in more thrilling and lasting form. If He shines out on us from the east that we have left behind, His brightness will paint the western sky towards which we travel. Beneath confidence in the perpetuity of past blessings lies confidence in the eternity of God. The "years of the right hand of the Most High" answer all questions as to His change of purpose or of disposition, and supply the only firm foundation for calm assurance of the future. Memory supplies the colours with which Hope paints her truest pictures. "That which hath been is that which shall be" may be the utterance of the _blasé_ man of the world, or of the devout man who trusts in the living God, and therefore knows that "There shall never be one lost good! What was shall live as before." The strophe in vv. 13-15 fixes on the one great redeeming act of the Exodus as the pledge of future deeds of a like kind, as need requires. The language is deeply tinged with reminiscences of Exod. xv. "In holiness" (not "in the sanctuary"), the question "Who is so great a God?" the epithet "Who doest wonders," all come from Exod. xv. 11. "[Thine] arm" in the psalm recalls "By the greatness of Thine arm" in Exodus (ver. 16), and the psalmist's "redeemed Thy people" reproduces "the people which Thou hast redeemed" (Exod. xv. 13). The separate mention of "sons of Joseph" can scarcely be accounted for, if the psalm is prior to the division of the kingdoms. But the purpose of the designation is doubtful. It may express the psalmist's protest against the division as a breach of ancient national unity or his longings for reunion.