There can be little doubt, however, that there are pre-exilic psalms or fragments in the Psalter. From Psalm cxxxvii. 3, 4 we may safely infer that already, by the time of the exile, there were songs of Jehovah or songs of Zion. We cannot tell what these songs were like; but when we remember that for nearly two centuries before the exile great prophets had been working--and we cannot suppose altogether ineffectually, for they had disciples--it is difficult to see why, granting the poetic power which the Hebrew had from the earliest times, pious spirits should not have expressed themselves in sacred song, or why some of these songs may not be in the Psalter. We appear to be on tolerably sure ground in at least some of the "royal" psalms. Doubtless it is often very hard to say, as in Psalms ii., lxxii., whether the king is a historical figure or the Messianic King of popular yearning; and possibly (cf. lxxii.) a psalm which originally contemplated a historical king may have been in later times altered or amplified to fit the features of the ideal king. Other psalms, again (e.g., lxxxix., cxxxii.), clearly are the products of a time when the monarchy is no more. But there remain others, expressing, e.g. a wish for the king's welfare (xx., xxi.), which can only be naturally referred to a time when the king was on the throne. It is not absolutely impossible to refer these to the period of the Hasmoneans, who bore the title from the end of the second century B.C.; but the history of the canon renders this supposition extremely improbable. The contents of these psalms are not above pre-exilic possibility, and their position in the first book would, generally speaking, be in favour of the earlier date. Psalm xlv. also, which celebrates the marriage of a king to a foreign princess, seems almost to compel a pre-exilic date.