Representation is when one thing is used in place of another. In any discussion on the nature of concepts, representation needs to be understood in order to understand the intentionality found in concepts.
Things may be representations in two ways. The first way is when something is always a representation. These are called words. Specific combinations of sounds, letters or hand-signs that pick out a concept of some kind. The second way is when something may represent, but also may not represent. These are the individual letters within words themselves. When written the letter “k” refers to a specific kind of sound. In the word “knife”, that sound is missing. There is no distinct contribution that the letter “k” gives to the word “knife” in terms of representing something. So while the word “knife” does represent a particular concept, the letter”k” in that word fails to represent anything at all.
There is no difference in the mark that forms “k” in either case. The reason for the difference is found outside of the mark. It is because there are human beings who place these marks in a particular context that they have the meaning they do. This means that representations are similar to concepts. They have the same rational intentionality that concepts have. However, representations are not the same as concepts.
Representations that are always representations are not the same as representations that represent of necessity. A red light in an intersection always means “stop” when it is lit. But there is no necessary connection between redness and the command to stop. We could have easily chosen to associate the color blue with the command to stop instead. We only always use that representation because that particular representation is never combined with another representation in order to represent a third concept. This second possibility is always an option as well.
Our written language is most like this. Each letter represents a specific sound. However, when these letters are combined in specific ways, something new is represented instead. Such a system is theoretically possible with colors. Simply have a certain set of colors represent something when they occur in the right order. Using such a system, it would be possible to create words that are formed out of colors rather than sounds or marks.
This means that concepts necessarily represent what they are pointing at while particular representations never do so. Concepts necessarily represent what they are pointing at because the act of pointing at that particular thing just is the concept. This means that concepts are mental acts. Representations are not mental acts. A series of letters on a page happen to be a representation of particular sounds, but they are not mental acts. They represent what they do because particular people have chosen to use them as a marker for a particular concept.
Now that we have examined the distinction between words and concepts, what about thoughts?