The Ten Modes of Aenisidemus

Aenesidemus compiled and systematized the following ten methods of examining any belief to identify whether it was unfounded.

1. Different animals manifest different modes of perception.
2. People have physical and mental differences, which make things appear different to them.
3. The different senses give different impressions of things.
4. Our perceptions depend on our physical and intellectual conditions at the time of perception.
5. Things appear different in different positions, and at different distances.
6. Perception is never direct, but always through a medium. For example, we see things through the air.
7. Things appear different according to variations in their quantity, color, motion, and temperature.
8. All perceptions are relative and interact one upon another.
9. Our impressions become less critical through repetition and custom. A thing impresses us differently when it is familiar and when it is unfamiliar.
10. The opinions and customs of people are different in different countries.