Physical and conceptual constructions are artifacts. 

Artifact is the word we use to describe our physical constructions. If knowledge is a human construction, then we could use this same word to describe our mental or conceptual constructions as well as our physical constructions. We are makers of artifacts, both physical and conceptual. If an artifact is any human construction, it could be a chair, a statue, a building, or a word, an idea, a concept, or even a theory. Force and species are artifacts like wheels and writing. Energy and molecule are artifacts just like automobile and house. Even a tree can be thought of as an artifact, for we construct trees in our minds to give coherence to a collection of experience. Whatever we fashion, from the simplest stone tool to the most complex theory, would thus be a human artifact. 

Conceptual artifacts can be the most general ideas we can make. 

Artifact is singular - a single word and a singular, external, individual, element. It can be very general, and it can represent any piece of knowledge that we fashion. Indeed, environments are artifacts, objects are artifacts, universals are conceptual artifacts, and of course, symbols are artifacts. An artifact - since it is anything we can fashion with our minds - is a larger idea than environment. Every environment is thus an artifact. The union of environments is also a human construction and would also be an artifact.

We can use physical construction analogies. 

Artifact is thus a fundamentally new tool for constructing knowledge. Imagine thinking about knowledge as the fashioning of conceptual artifacts, just as physical structures are the fashioning of physical artifacts. Our words become artifacts, our concepts become artifacts; our works of art, our designs, and our patterns will be constructed of artifacts. Our causes, our theories will be based on artifacts and not environments.

Artifact- knowledge is a human construction. 

When we invent new ideas we always start off by judging them both logically and psychologically. Artifact is a very large idea, it is a single word, and it is not made up - which means that we have powerful metaphors with which to explore these new realms. I like it psychologically because artifact forms knowledge as a human activity. It connects the construction of knowledge in the sciences with the artist and with the craftsperson. It brings with it ideas of beauty and building. And like any existing word which we could choose, it has its drawbacks. For we do define extraneous consequences as artifacts of the data. But from the first, I liked it. I found it compelling. I liked the feel ofit, the smell of it. And, in the beginning, that is all you have. For we have chosen a path on the flimsiest of evidence and the weakest of logics. But that is certainly what Einstein meant by "free invention." And that is what we always do with new ideas. Always! It is only when we have constructed the knowledge that our new words gain their naturalness and obviousness.

In which we define the nature of the central artifact of knowledge

If artifacts are the new entity, then by understanding artifacts we should both understand this new entity and have the basis for a theory of knowledge. What, then, will knowledge constructed of artifacts look like in this new period? We know from the Pattern of Knowledge that we will not be interested in the great variety of artifacts that can be built, just as the inventors of the Renaissance were not concerned about just any object. Rather, we will focus on special artifacts, on singular artifacts - on the ones that stand out - that we can build our theories and patterns on. This will be a singular phase of knowledge, and we would expect that there will be "central" artifacts.

Those are our most important artifacts.

Indeed, it is easy to argue that we already think this way; that singular, special artifacts in the physical and artistic world are the ones we pay attention and even homage to and always have. The buildings, the inventions, the physical objects, the artistic works, are the patterns that are special, rare, and beautiful - the objects of our attention and affection. We protect them, put them on display, and venerate them. These singular artifacts are distinct; they are rare; and we would say that they are unique. We make conceptual artifacts by the millions just as we do physical artifacts, and yet we choose only a few, only the special, the singular ones to pay real attention to.

The unique artifact is the key to knowledge. 

I would argue that these singular artifacts are unique. Something about them makes them rare, special, and valuable! We are constructors of unique artifacts!