These various values of the power of thought may be summed up in the following quotation from John Stuart Mill. "To draw inferences," he says, "has been said to be the great business of life. Every one has daily, hourly, and momentary need of ascertaining facts which he has not directly observed: not from any general purpose of adding to his stock of knowledge, but because the facts themselves are of importance to his interests or to his occupations. The business of the magistrate, of the military commander, of the navigator, of the physician, of the agriculturist, _is merely to judge of evidence and to act accordingly_.... As they do this well or ill, so they discharge well or ill the duties of their several callings. _It is the only occupation in which the mind never ceases to be engaged._"[3] [3] Mill, _System of Logic_, Introduction, § 5. § 2. _Importance of Direction in order to Realize these Values_ [Sidenote: Thinking goes astray] What a person has not only daily and hourly, but momentary need of performing, is not a technical and abstruse matter; nor, on the other hand, is it trivial and negligible. Such a function must be congenial to the mind, and must be performed, in an unspoiled mind, upon every fitting occasion. Just because, however, it is an operation of drawing inferences, of basing conclusions upon evidence, of reaching belief _indirectly_, it is an operation that may go wrong as well as right, and hence is one that needs safeguarding and training. The greater its importance the greater are the evils when it is ill-exercised. [Sidenote: Ideas are our rulers--for better or for worse]