Psychology, Philosophy, Economics, and Foreign Affairs Websites by Sam Vaknin The phrase “all cats are black” is evidently false even if only one cat in the entire universe were white. Therefore, the property “being black” cannot be part of the definition of a cat. The lesson to be learned is that definitions must be universal. They must apply to all members of a defined set (the set of “all cats” in our example). Let's try to define a chair. In doing so we try to capture the essence of being a chair, its “chair”. What is defined is the presidency, not this or that specific chair. We want to be able to identify the presidency whenever and wherever we encounter it. But chairability cannot be captured without addressing and somehow including the uses of a chair: what it is used for, what it does or helps to do. In other words, a definition must include a device, a function. In many cases the function of the Definiendum (the defined term) constitutes the meaning. The function of a vinyl record is its meaning. It has no meaning outside of its function. The Definiens (the expression that provides the definition) of a vinyl record includes and consists of its function or use. But is it possible to define a vinyl record in a vacuum, without incorporating the turntable into the definiens? After all, a vinyl record is an object containing audio information decoded by a record player. Without the “turntable” part, the definiens becomes ambiguous. It can contain an audio cassette or a compact disc. So context is essential. A good definition includes context, which serves to alleviate ambiguity. Apparently, the more detail provided in the definition, the less ambiguous it becomes. But this is not true. In fact, the more detail provided, the more ambiguous the definition tends to be. A definition must strive to be both minimal and aesthetic. In this sense it is very similar to a scientific theory. We talk about the correspondence or correlation between language and reality. Reality is parsimonious and to reflect it, definitions must be as parsimonious as they are. Let's summarize the characteristics of a good definition and then apply them and try to define some very trivial terms. First, a definition must reveal the meaning of the defined term or concept.