Aristotle's Categories

In creative problem-solving, checklists can provide an essential resource for examining the multiple aspects and qualities of a challenge, and for analyzing the elements that become the building blocks of a solution.

Arisotle's ten Categories list all the possible kinds of thing which can be, what he termed, the subject or the predicate of a proposition.

1. Substance or essence
What is it and what makes it unique or individual?
2. Quantity or magnitude
How many, how much, what degree?
3. Relation
Rank, comparison, derivation.
4. Quality
Value, attributes, shape, habits.
5. Action
What is it doing or does it do?
6. Affection
Reputation, attitudes toward.
7. Place
Where is it?
8. Time
When? (now? historical? future?)
9. Position
Sitting, standing, displayed, hidden.
10. State
Planned, broken, untried, changing.

Robert Harris explains how checklists can aid problem-solvers and decision makers in his book Creative Problem Solving.