A “simple” man is not an ordinary man. The Hebrew word implies the idea of being naïve. He believes what he is told. He takes what he hears “at face value” without measuring whether or not they are true. Everything is believable. He is rash in his decision-making and careless in his behavior. He is a gullible man, which is why Solomon says that he “believes everything.”
A modern-day analogy may be the person who is duped into thinking the need for what an infomercial is selling or that news is accurate just because it is spoken from a reporter on television.
The “prudent” man, by contrast, measures things with accuracy. He is, you might say, Berean (Acts 17:11) and always looking to measure what he hears according to what Scripture teaches.
The truth that resonates from this proverb is timeless. Jerry Bridges has said that “to believe every word of God is faith; to believe every word of man is credulity.”
In our day, there are so-called preaches claiming new revelation or additional interpretations that no one in church history have ever discovered. The “simple” will believe what he hears from preachers like this, because of their giftedness in communication or because the listener refuses to study out things he hears.
The Bible teaches us to test the spirits to evaluate whether or not they are from God (I John 4:1).
Don’t believe everything you hear and make sure everything you see is verifiable.