The art of thinking · Concepts, categories and definition
Essential and accidental properties
Also known as: Essence and accident, Essential property, Accidental property
In philosophy, an essential property is one a thing must have to be what it is, and an accidental property is one it happens to have but could lose without ceasing to be that thing.
- Thinking models
- Philosophy
In one sentence
Essential properties make a thing what it is; accidental properties are ones it happens to have and could lose without becoming something else.
Example
For a product family, “stops when the light curtain is interrupted” is essential to every variant with a light curtain; color, voltage and language of the HMI are accidental. Variant content sits in the accidental properties.
How it applies
- Aristotle: Essence is what is stated in the definition of a thing; accidents are what belong to it without being part of what it is — Socrates is essentially human and accidentally snub-nosed.
- Modern versions: Contemporary metaphysics usually spells the distinction out modally (a property the thing has in every possible situation in which it exists) and debates whether essences are real or a matter of how things are described.
- Description-relative in practice: What counts as essential depends on the kind under which a thing is described: for a “safety-rated light curtain” the safety function is essential, for “a light curtain” it may not be.
- Technical documentation: Separating the essential from the accidental is the core of variant management — common content describes what every variant must be, variable content what a variant happens to have. Safety-relevant differences are never accidental in the documentation, even when they look like options.
Essential properties vs. defaults
A default is the value a property has unless changed; it can still be accidental. Documenting a default as if it were essential creates the drift that configuration management has to repair later.
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