Relevant Alternatives Theory (RAT) is an epistemological theory of knowledge, according to which to know some proposition p one must be able to rule out all the relevant alternatives to p.

Introduction

Relevant alternatives theory was primarily developed by Fred Dretske

Fred Dretske

Frederick Irwin Dretske is a philosopher noted for his contributions to epistemology and the philosophy of mind. His more recent work centers on conscious experience and self-knowledge. Additionally, he was awarded the Jean Nicod Prize in 1994...

. It states that "knowing a true proposition one believes at a time requires being able to rule out relevant alternatives to that proposition at that time." One way that Dretske attempts to motivate RAT is with examples, such as the following:

You take your son to the zoo, see several zebras, and, when questioned by your son, tell him they are zebras. Do you know they are zebras? Well, most of us would have little hesitation saying that we did know this. We know what zebras look like, and, besides, this is the city zoo and the animals are in a pen clearly marked "Zebras." Yet, something's being a zebra implies that it is not a mule and, in particular, not a mule cleverly disguised by the zoo authorities to look like a zebra. Do you know that these animals are not mules cleverly disguised by the zoo authorities to look like zebras?

The relevant alternatives theorist claims that one does know that they are zebras, provided that any alternatives (e.g. the possibility of the zoo authorities cleverly disguising mules to look like zebras) are not relevant in the context in which knowledge is being attributed. The important question, however, is: What makes an alternative relevant?

External links

• "Epistemology" - an article by Matthias Steup on the Stanford Encyclopedia of Philosophy that discusses RAT primarily in §5.3.
• Dretske's Relevant Alternatives Theory - a short introduction by James Pryor at Princeton.