So to say that X exists when X is an object would be to say that an object that exhibits its physical properties has been observed?

And to say that X exists when X is the name of an idea is to say that somebody somewhere holds the idea in his or her mind?

So to say that X exists when X is an object would be to say that an object that exhibits its physical properties has been observed?

And to say that X exists when X is the name of an idea is to say that somebody somewhere holds the idea in his or her mind?

If X is an idea then, of course, someone has that idea. But that is not what it means to say that the idea exists.

I am confused. Does the act of holding an idea not cause the idea to exist?

If X is an idea then, of course, someone has that idea. But that is not what it means to say that the idea exists.

I am confused. Does the act of holding an idea not cause the idea to exist?

If X is an idea then, of course, someone has that idea. But that is not what it means to say that the idea exists.

This. To say the idea exists is not to say someone holds the idea? What is an idea if it is not held?

Yes, I am confused about that too.



So what is the criterion of existence for an idea? I suppose it depends on whether you define an idea as a "public" entity held by many people (e.g. the idea of time), or as a constituent of the mind of an individual (e.g. my current idea of the room I am in, or a sensation I am feeling). Either way, it seems that an idea can only exist if someone holds it. So I am puzzled by the underlined sentence above. Surely ideas are either constructed out of raw sense-data and/or other ideas, or received from other people who already hold the idea; they are not plucked out of some immaterial realm.

One other point. If we say that something exists if and only if it has properties, and that something has properties if and only if it exists (so that "imaginary" is not a real property of unicorns - see post #155), then the definition of "exist" is circular.

That an idea, I, is held, implies that that idea exists. But that doesn't, in any way, tell us what it means for the idea to exist.
If I own a dog, then the dog exists. But, that does not tell us what it means for the dog to exist. Does it?

---------- Post added 11-02-2009 at 08:32 AM ----------



1. It may be that the mental is the physical. The criterion is whether there is something which has the properties associated with ideas. As it is with everything else.

2. Not at all. It is a definition, and, so, if the definition is a true one, then the definiens, and the definiendum should be equivalent. Otherwise it is no a good definition. For example, Brother =df. male sibling. That is, if something is a brother, then that something is a male sibling: and if something is a male sibling, then it is a brother. That isn't circular. It is a true definition.

A circular definition is one in which the definiendum is defined by itself or a near synonym. E.G. "Interesting" means, "attracts your interest".

If you have an idea, the idea exists. No one has denied that.

But some may hold that if something doesn't physically exist, or is not a part of the physical world, it doesn't really exist. We can reduce ideas to the mind, and the mind to the material brain, but the material brain is not the idea itself. Ideas and concepts are merely secondary, epiphenomena. They don't exist in the same sense that my hand does. The only problem I see with this is that it either calls for making a distinction between two categories of existence, or it demands that ideas be considered not to exist or not to be real.

Ideas exist in exactly the same sense your hand exists. That is, they have properties, and your hand also has properties. It may, of course, be, that your hand has physical properties, but that ideas do not have physical properties. But that doesn't mean that the sense in which they exist is different. I just means that to discover whether each of them exists, you have to look for different kinds of properties each instantiates.

Can you please describe the properties of an idea?

Certainly. An idea may be: interesting, new, belong to me, be very influential, and so on. One idea may give birth to another idea, also.

But none of these terms you use refer to physical properties. You're simply using abstract concepts (belong to me, interesting, new) to support another abstract concept.

Well, ideas are mental, they are not physical. So why would you expect them to have physical properties? An idea may be vivid rather than weak, detailed or specific, rather than vague. Physical objects do not have mental properties either. All concepts are abstract.

I know that all concepts are abstract, but that's my point. The mind is simply the word we use to describe the functional process of the brain. The brain is material, but the material brain is not the idea itself. Are not mental constructs nothing more than the functions of the material brain?

I am not convinced that abstractions are worthy of the classification of existence. Maybe I'm being too rigid, but I don't feel like I mean the same thing when I say that abstractions exist and when I say that my eyeball exists.