But further; the absence of knowledge is sure to be something more and worse than simple ignorance. Even were that absence but a mere negation, a vacancy of truth, (the terms truth and knowledge may be used for our present purpose as nearly synonymous, for what is not truth is not knowledge,) it would be by its effect as a _deficiency_, incalculably injurious. But it could not remain a mere deficiency: the vacancy of truth would commonly be found replenished with positive error. Not indeed replenished, (we are speaking of uncultivated persons,) with a comprehensive and arranged set of false notions; for there would not be thinking enough to form opinions in any sufficient number to be distinctly and specifically the opposites to the many truths that were absent; but a few false notions, such as could hardly fail to take the place of absent truth in the ignorant mind, however crude they might be, and however deficient for constituting a full system of error, would be sure to dilate themselves so as to have an operation at all the points where truth was wanting. It is frightful to see what a space in an ignorant mind one false notion can occupy, working nearly the same effect in many distinct particulars, as if there had been so many distinct wrong principles, each producing specifically its own bad effect. So that in that mind a few false notions, and those the ones most likely to establish themselves there, shall be virtually equivalent to a whole scheme of errors standing formally in place of so many truths of which they are the reverse. And thus the dark void of ignorance, instead of remaining a mere negation, becomes filled with agents of perversion and destruction; as sometimes the gloomy apartments of a deserted mansion have become a den of robbers and murderers. Such a friend of the people, then, as we were supposing to expend his life and zeal on the object of rescuing them from their ignorance, would see in that ignorance not only the privation of all direction and impulsion to good, but a great positive force of determination toward evil.