Sense vs. Reference

Sense is the thought expressed by a word, independent of context: the means by which a word refers to something in the world. Reference is what a speaker intends to pick out through the use of an expression, and it is partly determined by contextual factors. Words may share a reference while differing in sense.

The Morning Star and the Evening Star

A classic illustration is the morning star and the evening star. Both are Venus, so the reference is identical in each case: Venus appears in the morning and again in the evening, which is why both descriptions arose. People used the two names without always realizing they picked out the same object, and indeed without realizing it was not a star at all. The expressions referred to one and the same body while describing it in two different ways, so they differed in sense though not in reference.

The same holds within a single event. The bear escaped from the zoo and the bear ran away from the zoo can pick out the very same event, yet their meanings are not identical because run away has a slightly different sense from escape. Likewise the large black furry carnivorous animal escaped from the zoo can refer to the same animal as the bear; the reference is one entity, but the describing words differ. Sense is the thought used to point at something; reference is what is actually pointed at.

Reference Without an Object

Because sense is distinct from reference, a sentence can contain a word that has no reference and still be understood. The unicorn escaped from the zoo contains unicorn, which picks out nothing in the real world, yet the sentence is still meaningful: one knows what the world would have to be like for it to be true. This shows that a word's meaning is more than its reference; the absence of a referent does not erase the sense.

This differs from a sentence being merely false. If the lion escaped from the zoo is uttered when a lion is present but the bear is what escaped, the sentence is simply false. Philosophers have long debated whether a sentence like the unicorn escaped from the zoo is true, false, or neither when a referent is missing, but that debate is beside the present point. What matters is that sense and reference can be separated, since sentences with non-referring terms remain intelligible.