But observation and material inference are subject to the limitations of our faculties; and however we may aid observation by microscopes and micrometers, it is still observation; and however we may correct our observations by repetition, comparison and refined mathematical methods of making allowances, the correction of error is only an approximation to accuracy.

Outside of Formal Reasoning, suspense of judgment is your only attitude.
But such objections imply that nothing short of absolute truth has any value; that all our discussions and investigations in science or social affairs are without logical criteria; that Logic must be confined to symbols, and considered entirely as mental gymnastics.

In this book prominence will be given to the character of Logic as a formal science, and it will also be shown that Induction itself may be treated formally; but it will be assumed that logical forms are valuable as representing the actual relations of natural and social phenomena.
Sec.7.Symbols are often used in Logic instead of concrete terms, not only in Symbolic Logic where the science is treated algebraically (as by Dr.
Venn in his _Symbolic Logic_), but in ordinary manuals; so that it may be well to explain the use of them before going further.
It is a common and convenient practice to illustrate logical doctrines by examples: to show what is meant by a Proposition we may give _salt is soluble_, or _water rusts iron:_ the copulative exponible is exemplified by _salt is savoury and wholesome_; and so on.

But this procedure has some disadvantages: it is often cumbrous; and it may distract the reader's attention from the point to be explained by exciting his interest in the special fact of the illustration.

Clearly, too, so far as Logic is formal, no particular matter of fact can adequately illustrate any of its doctrines.