Neirai the Forgiven
Christian Guilds List Manager
A decent chunk of Proverbs were actually written long before Solomon's time, in a region that did not follow our God. Universal Truths are universally true... that is, they do not depend on a specific time, place or person to apply.
To further comment on this idea, back before people had jobs, there was a system known as "patronage." Under they patronage system, if a ruler or noble was (or considered themselves) a notable artist or art critic of some sort, and also enjoyed a great variety of art, artist of that type would congregate to their courts in order to get money by presenting art to the "patron."
For example, in the Renaissance, England's Queen Elizabeth I was an accomplished poet; her court soon became packed with poets who hoped to win her favor, which brought with it money and fame.
According to Historical criticism, Solomon, being the wisest king ever, probably attracted to his court wise sages from around the world, which is why the world's greatest non-Judaic wisdom is found nestled inside the proverbs.
Fortunately, Solomon was wise enough to discern which sayings were Universal Truths, that is, that they were the words of God, even though they came through the unbelievers.
Just like Queen Elizabeth I would critique her poets' works, so would Solomon. In this way, pagan knowledge that flew in the face of truth would be stress-tested and eliminated.