Full Idea
If a circle is defined as a figure in which lines from centre to circumference are equal, such definitions do not explain the essence of a circle, but only a property. The properties of a thing are not understood as long as their essences are not known.
Gist of Idea
To understand the properties we must know the essence, as with a circle
Source
Baruch de Spinoza (Improvement of Understanding [1675], §95), quoted by Cover,J/O'Leary-Hawthorne,J - Substance and Individuation in Leibniz 1.2.1
Book Reference
Cover,J/O'Leary-Hawthorne,J: 'Substance and Individuation in Leibniz' [CUP 1999], p.24
A Reaction
This is the traditional Aristotelian view of essence, and the example of a circle is nice, though I am not sure what the essence of a circle might be. Presumably ALL the properties of a circle must flow from it.
Related Ideas
Idea 13432 The essence of a circle is the equality of its radii [Leibniz]
Idea 13431 A space between three lines is both the nominal and real essence of a triangle, the source of its properties [Locke]