Examples:

1. For animals their environment consists primarily of affordances: things they can mate with, eat, shelter.

Insights:

1. Every human and animal has a set of things in the world that matter to it, that it can use.

Insights:

1. Don't create a complicated theory, if a simpler one exists.

References:

1. Attributed to William of Ockham, 14th centure philosopher.
2. The rule of thumb is much older: Latin lex parsimonie, the law of parsimony.