Subject: RE: essential definitions

My replies are inserted below.

-----Original Message-----

Sent: Sunday, February 13, 2000 7:21 PM
To: klima@murray.fordham.edu
Subject:


Regarding the Isagoge:
1) What is an essential definition?  i.e. why would we need to identify
substantial concepts in terms of other unrelated concepts to obtain an
essential definition of that singular concept (page 95)?  Does this passage
refer to different ways of looking at “water,” for example, on a chemical
and non-chemical basis? -- in which case it would be looking at the same
concept from different perspectives and not two concepts after all.

-------------------------------

An essential definition (as opposed to a nominal definition, which merely stipulates or describes the meaning of a term) is a complex phrase that provides a description of the nature of the kind of thing referred to by the term defined in terms of the thing’s essential predicates, its genera and specific differences. For example, the term ‘water’ refers to a certain kind of thing which we normally recognize on the basis of its being a transparent, thirst-quenching, drinkable liquid. But these properties are obviously not essential properties of water, for water is still the same kind of thing when it is not liquid (e.g., when it is frozen), or when there is no one to drink it, etc. However, if what we can learn from chemistry about water is right, then water is indeed a compound consisting of H₂O molecules, and the kind of thing we call ‘water’, necessarily has these properties as long as it exists, namely, that it is a compound (genus) and that it consists of H₂O molecules (specific difference). But then, knowing this definition obviously enables us to make true, scientific claims concerning any water sample in any circumstances in which it exists, which is why we are looking for such essential definitions in science.

----------------------------


2)  Why must essential attributes be different form the substantial
forms, e.g., in chemistry we say H₂O IS water -- not an essential attribute of
the universal form of water (this latter definition makes the formula of
water a quality of some unattainable, vaster concept of water).  I would say
H₂O is the substantial form of water and the essential forms or attributes
are its phase changes, boiling point, melting point, etc.

-------------------------

Do not mistake names for what they signify and what they refer to. Attributes are linguistic entities: names, symbols, formulae, etc., which have the function of signifying the inherent properties, or as Aristotle would have it, inherent forms of the things they refer to. For example, the English term ‘water’, as well as the Latin term ‘aqua’, and the chemical symbol ‘H₂O’ have the same function, namely, to signify the substantial form of the thing we refer to as ‘water’ in English, as ‘aqua’ in Latin, and as ‘H₂O’ in chemistry. It is also the same form that is signified by the essential definition (if it is correct): ‘a compound consisting of H₂O molecules’. (Note that the formula here does not have the function of referring to a body of water as in the sentence ‘This glass contains H₂O’, but to briefly specify the structure of the molecules indicated in the definition.) I am going to tell you more in class about the relationships between essential predicates and the substantial forms signified by them, as opposed to accidental predicates and the accidental forms signified by them, once we get to Aquinas’s treatise “On the Principles of Nature”. Meanwhile you may also want to look into my Yale Lecture “Aquinas on being and essence”, printed in your course packet, for further clarification.