The greatest deception men suffer is from their own opinions.

Hear, O seeker of truth, the words of the master of invention and painter of the eternal light, Leonardo da Vinci: “The greatest deception men suffer is from their own opinions.” These words are not idle musings of a mind at rest, but the hard-won wisdom of a man who gazed deeply into the nature of reality, who knew that the gravest prison is not built of stone or iron, but of the illusions a soul weaves around itself. To be deceived by others is a wound inflicted from without, yet to be deceived by one’s own mind is a wound that festers within, unseen yet ever-consuming.

The meaning of this teaching is profound. Men hold fast to their judgments as if they were shields of iron, yet often these judgments are but shadows, born of ignorance, fear, and pride. Opinions are the child of limited vision; they are formed not from the whole truth but from fragments. Thus, when a man believes his opinion to be truth itself, he walks blindfolded into folly. This, Leonardo warns, is the greatest deception—for no enemy can so thoroughly conquer us as the lies we tell ourselves.

Consider the fate of mighty nations that have fallen, not from external foes, but from the arrogance of their own beliefs. Did not the city of Troy burn because its rulers trusted too greatly in their own certainty, refusing to see the danger hidden within the wooden horse? Their opinion—that they had triumphed—was their undoing. So too do men, in their daily lives, mistake their own limited view for wisdom, only to suffer ruin when the truth reveals itself too late.

In more recent times, think upon the story of the Titanic, the so-called unsinkable ship. Its builders and passengers alike placed their faith in the opinion that no force of nature could breach its hull. That belief became their shroud. In the icy waters of the Atlantic, human arrogance was humbled, and thousands paid with their lives. Here again is the truth of Leonardo’s words: the deceptions born of our own opinions can destroy more swiftly and completely than any falsehood told by another.

Yet do not despair, for wisdom lies not in never holding opinions, but in knowing their limits. The wise man holds his thoughts lightly, as one holds water in the palm of his hand—never grasping so tightly that the truth slips away. To doubt oneself is not weakness; it is strength, for it opens the door to learning, growth, and the correction of error. To question one’s own mind is to keep alive the flame of discovery, as Leonardo himself did in all his studies, ever challenging what he thought he knew.

The lesson for us, then, is clear: do not worship your own beliefs. Test them against reason, against evidence, against the wisdom of others. Seek always to learn, for the moment you believe your own opinion to be infallible, you are already ensnared in deception. Humility is the shield that guards against the falsehoods of the self.

As for practical action, let every man and woman practice the art of questioning. When you are certain, ask: “What if I am wrong?” When you feel unshakable in judgment, seek the counsel of another perspective. Read widely, listen deeply, and let curiosity dissolve the walls of your self-made prison. Above all, hold truth above pride, for pride is the soil in which deception grows most swiftly.

Thus, remember always the voice of Leonardo: the mind can be its own betrayer. Guard it well, with humility, with inquiry, and with the courage to let go of falsehood. For the one who conquers the deceptions of their own opinions is not only free but powerful, able to see reality as it is, and to live in harmony with truth.