For a homework I have been ask to prove that if a theory $\Sigma$ over a vocabulary $L$ has a model with countable domain, then $\Sigma$ has a model with uncountable domain.
I have no idea how to proceed, any suggestions are welcome.
Thanks.
For a homework I have been ask to prove that if a theory $\Sigma$ over a vocabulary $L$ has a model with countable domain, then $\Sigma$ has a model with uncountable domain.
I have no idea how to proceed, any suggestions are welcome.
Thanks.
Hint: Add to the theory uncountably many new constant letters, plus axioms stating that they are pairwise different. Now use compactness.