An investment operation is one which can be justified on both qualitative and quantitative grounds.
An investment operation is one which, upon thorough analysis, promises safety of principal and a satisfactory return.
Thorough Analysis: The study of the facts in the light of established standards of safety and value.
Safety: Protection against loss under all normal or reasonably likely conditions or variations.
Satisfactory Return: Any rate or amount of return, however low, which the investor is willing to accept, provided he acts with reasonable intelligence.
(Security Analysis, 1940)
To have a true investment there must be present a true margin of safety. And a true margin of safety is one that can be demonstrated by figures, by persuasive reasoning, and by reference to a body of actual experience.
(The Intelligent Investor, 1949)