Manly P. Hall begins by shifting the student from metaphysics—the study of first principles—to logic, the second great division of philosophy. He argues that “fact” is largely a human convenience, since absolute fact is inaccessible, and modern knowledge rests on relative fact. Logic, originally the science of correct thinking, has become overly technical in modern times, but its classical foundation remains rooted in Aristotle’s system. Hall explains the three instruments of logic—analogy, induction, and deduction—and demonstrates how each operates by moving between particulars and universals. These processes, he says, underlie the formation of philosophy (analogical reasoning), science (inductive reasoning), and religion (deductive reasoning). Logic’s purpose is to establish mental equilibrium by relating the mind to equals, superiors, and inferiors, thereby producing balanced judgment.

In the second half of the letter, Hall turns to the practical value of logic in daily life. He distinguishes logic from consistency, noting that consistency refers not to the reasoning process but to the alignment between one’s conclusions and one’s actions. Emerson’s critique of consistency as mental rigidity is addressed: Hall agrees that growth requires the courage to abandon outdated beliefs, but insists that inconsistency arises only when a person attempts to live by contradictory standards. True consistency means living in harmony with one’s logically established values. Logic provides the framework for determining principles such as honesty, while consistency ensures that one’s conduct reflects those principles. Hall concludes by urging the reader to think clearly, establish sound premises, and live in coordinated alignment with those conclusions—“Think logically and live consistently.”