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Variables – this refers to x, y, and z. So, basically like anything in the world.
Constants – this refers to particulars. So, particular individuals in the world. So, we symbolize it
as “a to w”.
Bound Statements or Bound Variables – these are variables with Quantifiers. So, in “(x) (Mx ⊃
Ox)”, “(Mx ⊃ Ox)” is a Bound Statement because as you can see, you have here a Quantifier,
which is “(x)”.
Free Statements or Free Variables – these are something then without Quantifiers. So, an
example is “Mx ⊃ Ox”. If you don’t have a Quantifier that is a Free Statement.
Instantiation – this is the process we use when we remove Quantifiers. When we remove
Quantifiers, we are Instantiating, and the letters that we use when we do that are called
“Instantial Letters”. So, it could be a Variable (x, y, z), we can Instantiate using a Variable or using
a Constant (a-z), depending on the Rule. This depends on the rule as I will discuss in a while. There
are some Rules that prohibit you from Instantiating certain Instantial Letters. So, here, from a
Bound Statement, we’re making it a Free Statement.