What is an abstraction? According to the concept of a concept just discussed, we can observe that an abstraction is one element of a concept, but as a definition that would be circular. A dictionary definition of "to abstract" is "to consider apart from application to or association with a particular instance" (Merriam-Webster's Collegiate Dictionary, Tenth Edition). For purposes of this document, I will define an abstraction as a set of objects and a set of operations on the objects. This is in fact the way a data abstraction (a.k.a. an abstract data type or simply a type) is usually defined in computer science, but actually the definition is broad enough to capture also a notion of algorithms (an abstraction in which there is only one operation, the algorithm, in the set of operations and the set of objects is usually empty) and other fundamental computer science terms. It may seem a stretch to apply the computer science definition to other non-computational domains, but let's plunge ahead with this tactic for the time being anyway. After all, according the goals of the nascent informatics program at Rensselaer, we are trying to see how large parts of the domains of science and the arts can be fruitfully viewed with the aid of a computational perspective.