To give subtlety to the simple,.... Men of mean abilities, weak capacities, shallow understandings, incautious, credulous, and easily imposed upon: these, by attending to what is herein contained, may arrive to a serpentine subtlety; though they are simple and harmless as doves, may become as wise as serpents; may attain to an exquisite knowledge of divine things and know even more than the wise and sage philosophers among the Gentiles, or any of the Rabbins and masters of Israel; or any of the princes of this world, whose wisdom comes to nought; and become very cautious and circumspect how they are drawn aside by the old serpent the devil, or by such who lie in wait to deceive; and perform their duty both to God and man;to the young man knowledge and discretion; or "thought" ; who wants both: this book will teach him the knowledge of things moral, civil, and religious: to think and act aright; how to behave and conduct himself wisely and discreetly before men; and be a means of forming his mind betimes for piety and religion; and of furnishing him with rules for his deportment in future life, in all the periods of it; and in whatsoever state and condition he may come into.
A "young man [may] cleanse his way", Ps 119:9, reform his manners, behave with purity and uprightness, by taking "heed" to the things herein contained.