Philosopher E.J. Lowe states that

There is a clear difference between saying something like ‘Rover is a dog’, in which we assign Rover, a particular animal, to a certain natural kind or species, and saying something like ‘Rover is brown’, in which we attribute a certain property or quality to Rover. Modern first-order predicate logic completely obliterates this distinction, representing both sentences as having the logical form ‘Fa’.

However it is not so clear to me what the difference is between property ("brownness") and kind ("dog"). Couldn't we consider "dogginess" as property and "brown" as a kind? What is the difference ontologically?

  • The notion of natural kinds arise out of Aristotles onto-logic - genus and species; formal logic simply by its formality erases ontology; one might suggest, in same way that mathematical formalism erased the ontology implicit in mathematical Platonism. Commented Feb 8, 2016 at 20:43

2 Answers 2


The difference is that children at Halloween and in school plays can also get dogginess, and that simply "being brown" brings along no additional information. The whole nature of "natural kinds" is that 1) they cannot be obtained artificially and 2) they bring in a whole family of related traits also.


The difference is that it appears Rover could survive the change of the one property but not the other. If the dog gets painted, he continues to live. Change Rover into something else a statue, say, and Rover ceases to exist.

  • 1
    Why assume that Rover ceases to exist? What if Rover were transformed into a human being? He would not cease to live for sure. He would still exist and be Rover, but instantiating the property of humanity instead of dogginess.
    – Adrian
    Commented Feb 8, 2016 at 21:12
  • 1
    Lowe thinks Rover would cease to exist under those situations. He might be wrong about that, but those are the "intuitions" that he's choosing to build the rest of his metaphysics around. If you think those are the wrong intuitions, you have good reason not to want to follow him down the rest of the path. But Lowe thinks that lots of people would share those intuitions.
    – user5172
    Commented Feb 8, 2016 at 21:52

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .