Atom (Logic)

Atoms are the building blocks of propositional logic, and are used to form more complicated propositions. As the name suggests, they cannot be broken down further into sub-propositions. Like a proposition, they can only be either true or false (but not both, or none).

Conventionally, they are denoted with uppercase variables starting from $P$, i.e. $P,Q,R,S\dots$

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Some examples of atoms:

• $P=2\text{ is even}$
• $Q=\text{It will rain tommorrow}$
• $R=3+9>32$

Again, a statement doesn’t necessarily have to be true for it to be a proposition.

The truth table for a proposition is:

$P$
T
F