After hearing incessantly that the people follow him without sense or discretion, he [the political leader] is liable to fall a victim of the delusio… - Alexander Bryan Johnson

Locke supposes that a person acquainted sensibly with the colours which compose a rainbow, can by the names of such colours in a verbal description, be made visually acquainted with a rainbow. The verbal description will give such a person's intellect a good verbal definition of the word rainbow, but it cannot communicate the sight to the extent that it differs, in any manner from the sights he already knows.

A young lady, being on a visit at a noble friend's mansion, was betrayed by complaisance into an admission that she was very fond of potted sprats, though she abhorred the sight, taste, and smell of them. This little falsehood brought her into a false position as respects her noble friend, who, to oblige her young guest, provided for her nothing but potted sprats. ...So the aforesaid young lady found herself suddenly seated beside a plate of sprats, with all their disgusting odours rising to her face, and their horrid forms spread out before her eyes. A moment ago, she might, with entire propriety, have declared her disgust of them; but she had taken her false position, and that was now to govern. ...But here the authority ended of all external government. The chyle would not digest the intruder, nor the pylorus permit its egress The whole inner woman suffered a state of rebellion; when a new actor appeared upon the stage... in the shape of fever, first mild and gentle, then importunate and bold, then raging, and then outrageous. The fever introduced, in turn, a new agent in the shape of a physician, grave and knowing; who introduced two others more knowing still, who introduced various cathartics, diaphoretics, lancets, leeches, blisters, and glysters, which together soon introduced debility, epilepsy, and catalepsy; which, to the astonishment of no one but the doctors, introduced death, who ended the false position.

All that the book contains is the elucidation of but one precept: namely, to interpret language by nature. We [generally and incorrectly] reverse the rule and interpret nature by language.