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Specifically my main problem, and the reason I cant translate this on my own is because Im curious if the Washington Monument would be a subject too like Michael so would it be a lower case letter or can only people be subjects the answer I think it is is

I=incorrect m=Michael W=Washington Monument G=made of granite Hence: Im --> WG

Also in the answer I think is right Im just assuming Washington monument is a predicate because I still dont know if objects can be subjects in predicate logic.

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  • It is not the case that only people are subjects in predicate logics, when you use logic you decide on a "domain of discourse" which are the things that you're using as subjects. When translating natural language into a logic, the domain of discourse is usually just "all things" which means all objects can be subjects in your sentences. The Washington Monument should be treated as an object and the predicate is "made of granite".
    – Not_Here
    Commented Nov 16, 2017 at 0:11

1 Answer 1

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The sentence you currently have is not well-formed. Specifically, ‘WG’ isn’t well-formed if ‘W’ and ‘G’ are both predicates. The English equivalent of a first-order predicate would be an expression like ‘is white’, ‘is happy’, or indeed ‘is made of granite’. In turn, just like you can’t say ‘Is happy is white’ in English, you can’t say ‘WG’ in logic. (You can say e.g. ‘Being rich is nice’, and thus effectively apply one predicate to another. However, in this example one of the two predicates acts as a second-order predicate, while the other is first-order.)

Now, there is a view that English names are actually predicates. (On that view, ‘Michael’ is actually a predicate in disguise, viz. roughly ‘is called Michael’.) However, in logic we normally use individual constants to translate names. When combined with a predicate, constants can then be used to translate e.g. ‘Michael is incorrect’ and ‘the Washington Monument is made of granite’.

What’s confusing about ‘the Washington Monument’ is that it contains the definite article ‘the’ – just like e.g. ‘the café on 3rd street’, which is definitely not a name and shouldn’t be translated using an individual constant. Still ‘the Washington Monument’ is essentially a name or a proper noun as some prefer to say.

One (not infallible) way to test this is by imagining a tourist looking at the monument and asking: ‘What’s the name of that?’ It seems perfectly fine to reply with: ‘It is called ‘The Washington Monument’’. By contrast, if the tourist points at the café on 3rd street and asks: ‘What’s the name of that?’, it would be weird to answer: ‘It is called ‘the café on 3rd street’’ – unless of course the café’s owner has decided to bestow this rather unimaginative name on her café.

Another way to test whether an expression is a name, is by asking whether the expression is being used to describe, or to refer. Here’s an example that may make that a little clearer: perhaps my address is 17 Oxford Circus. Now, Oxford Circus is neither in Oxford, nor is it a circus. So, ‘Oxford Circus’ isn’t used to describe the place, but to refer to it. It's therefore a name. By contrast, if I say: ‘A giraffe has escaped from (the) Oxford circus’, I am using ‘Oxford circus’ to describe where the giraffe escaped from: I’m describing it as a circus in Oxford. (Pub names are another great example: The Golden Lion is presumably neither golden nor a lion.)

As a final remark, as far as logic is concern literally anything can be given a name: people, places, buildings, streets, pieces of furniture, individual molecules, galaxies – just anything. In fact, even names can bear names.

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