Abstract
In the representation we end up with, concepts are like "nodes" in a conceptual network, and the relationships between nodes represent not only the analytical implications of concepts - the fact that red is a color, or that bachelors are unmarried - but also the contingent connections that are established between concepts at the level of encyclopedic knowledge - the fact that ripe tomatoes are red, and bachelors are less homely than married people, for example.
If we put into the content of a concept everything we know or think we know about the objects that fall under the concept, and if we maintain the idea that the content of a concept is what makes it the concept that it is, then we have to accept that every time a change in our encyclopedic knowledge about the objects in question occurs, we change concepts - one concept is substituted for another. This consequence is unacceptable, as it jeopardizes a fundamental property of concepts: their stability.
As constituents of thought, concepts are essentially combinable. Because they are essentially combinable, concepts must be repeatable: the same concept must be able to appear in several distinct thoughts, combined with various other concepts. This conceptual repeatability is exploited in both theoretical and practical reasoning. A concept must also remain the same from one subject to another, so that there can be rational discussion and agreement or disagreement: disagreement between two people implies a sharing of thoughts (for one and the same thought, one subject holds it to be true and accepts it, while the other rejects it), and therefore the interpersonal stability of the concepts that are the constituents of these thoughts. In the same way, the change of opinion of one and the same person requires the sharing of thoughts, and therefore concepts, between the person who judges today that P and the person he or she was previously, who judged that P was not true.
In order to safeguard the intra- and interpersonal stability of concepts, while maintaining the encyclopedic conception of concept content, we have to abandon the idea that the content of a concept is what makes it the concept that it is. We need to distinguish between the concept and the content of the concept ("conception"). The concept is independent of the conception, in the sense that the conception can change, even radically, without our ceasing to deploy the same concept. When we change our mind on a given subject, our conception changes, but the concept remains stable. This means that the identity of a concept is not a function of its content, but of something else. What is that something else?
According to the "referentialist" thesis, what individualizes a concept, what makes it the concept that it is, is not the concept's content but its reference, i.e. what the concept is the concept of. Two concepts are the same if and only if they refer to the same thing.
