A criterion of investment vs. speculation:

Many see no benefit in distinguishing the investor from the speculator.

Graham disagrees -- he believes the margin of safety may be "the touchstone to distinguish an investment operation from a speculative one." 

The speculator believes the odds are in their favor when they take their chance and they might claim a margin of safety as a result from a propitious time, skill in analysis, adviser or system, etc. But these claims are unconvincing.


http://www.conscious-investor.com/books/intelligentinvestor.pdf

The investor's concept of a margin of safety

 The investor's concept of a margin of safety rests upon a simple and definite arithmetical reasoning from statistical data.

1. There is no guarantee that the fundamental quantitative approach will be successful in the future, but no reason for pessimism. 
2. "To have a true investment there must be present a true margin of safety." 

"It is our argument that a sufficiently low price can turn a security of mediocre quality into a sound investment opportunity--provided

• that the buyer is informed and experienced and 
• that he practices adequate diversification. 

For if the price is low enough to create a substantial margin of safety, the security thereby meets our criterion of investment.


http://www.conscious-investor.com/books/intelligentinvestor.pdf