'Simple' in the Bible

I am speaking in simple terms because of the frailty of your human nature. Just as you once offered the parts of your body as slaves to impurity and to greater and greater disobedience, so now, in the same way, you must offer the parts of your body as slaves to righteousness that leads to sanctification.

For they that are such serve not our Lord Jesus Christ, but their own belly; and by good words and fair speeches deceive the hearts of the simple.

For your obedience is come abroad unto all men. I am glad therefore on your behalf: but yet I would have you wise unto that which is good, and simple concerning evil.