shall i use the definite article here?
Can you distinguish the good from the bad?
He can’t distinguish the good from the bad let alone get married

the good from the bad / or just good from bad?

Question

shall i use the definite article here?
Can you distinguish the good from the bad?
He can’t distinguish the good from the bad let alone get married

the good from the bad  / or just good from bad?

Answer

The good from the bad. I’m assuming you are talking about a prospective wife/women.
He can’t distinguish the good (women) from the bad (women).
If you said he can’t distinguish good from bad this means he can’t determine what is good and what is bad (morally good/bad).