The objections to the Solomonic age as the time of origination of the book apply also to the period extending from Solomon through the 6th century.
The supposition of a Solomonic authorship for Proverbs is excluded by the whole colouring of the book, in which monotheism and monogamy are assumed, without discussion, to be generally accepted, while in Solomon's time and by Solomon's self the worship of many gods and the taking of more than one wife were freely practised, without rebuke from priest or prophet.
The Solomonic authorship has long since been given up: the historical setting of the work and its atmosphere - the silent assumption of monotheism and monogamy, the nonnational tone, the attitude towards kings and people, the picture of a complicated social life, the strain of philosophic reflection - are wholly at variance with what is known of the 10th century B.C. and with the Hebrew literature down to the 5th or 4th century B.C. The introduction of Solomon, the ideal of wisdom, is a literary device of the later time, and probably deceived nobody.
With his wide linguistic knowledge Eichhorn perceived that the language alone (though he also adduces other considerations) betrays the late origin of Ecclesiastes, which he places in the Persian Period (538-332 B.C.): Canticles, too, preserves linguistic features which are not of the Solomonic age.