- A priori knowledge or justification is independent of experience (for example "All bachelors are unmarried"). Galen Strawson has stated that an a priori argument is one in which "you can see that it is true just lying on your couch. You don't have to get up off your couch and go outside and examine the way things are in the physical world. You don't have to do any science."
- A posteriori knowledge or justification is dependent on experience orempirical evidence (for example "Some bachelors I have met are very happy").