Ne sutor ultra crepidam

The shoemaker should not go beyond his last. Men should not attempt what they are neither by education nor genius qualified to perform, nor discourse on matters they do not understand; they will be listened to with no more attention than would be given to a blind man discoursing on colours. Cada qual hable en lo que sabe, let every one talk of what he understands. A shoemaker having suggested to Apelles an error in the form of a shoe he had painted, the artist, readily taking the hint, altered the picture in that part. But when the same shoemaker was proceeding to recommend alterations in the form and disposition of the limbs of the figure, he received the rebuke, which thence became proverbial, "The shoemaker should not meddle beyond his last." Defiéndame Dios de mí. God defend me from myself, the Spaniards say, make me to know what is my proper state and condition.