Type a boolean expression
(identifiers, parentheses, and operators
'and', 'or',
'->', 'not')
in the Wff area of the HTML FORM below and press the 'go' button.
Experiment.

Remember, there are three possible outcomes:
A Wff is either
a tautology (always true),
a contradiction (always false), or
satisfiable (sometimes true, sometimes false).

Exercises

What kind of Wff leads to the greatest expansion
when it is converted into CNF?

Ditto DNF?

Some advertising relies on the following kind of "reasoning": People who are (rich | powerful | attractive | etc.) buy XXX,
therefore if you buy XXX you will
become (rich | powerful | attractive | etc.).

Is this kind of "reasoning" valid?

Consider: People who are [whatever] buy food;

Formulate the advertising "reasoning" as a Wff and
use the FORM to see the true situation.

Give a related but different kind of reasoning with a different outcome.

Notes

Read the [propositional logic] page
to learn more about the algorithm
used on the HTML FORM above.

The programming language Prolog
is based on the more powerful Predicate Logic.
There is a demonstration Prolog interpreter
[here...].