Contrast between the two adjectives suggest that Eric is not a fully-formed individual. He is suspended between being product of his Capitalist parents and his own person.
Perhaps he is weak-willed, living in the shadows of his father.
"you killed her - and the child... your own grandchild"
Priestley encourages the audience to sympathise with Eric
Despite the Inspector attempts to enlighten the family that they are all jointly responsible, Eric's accusation of blame upon his mother is tantamount to Mrs Birling's blame of the "father"
Eric attempts to absolve himself from any blame
"She wasn't the usual sort... she didn't know what to do"
"usual" - implies that visiting prostitutes was a norm for Eric
Eric's observation that "she didn't know what to do" implies both that he is attracted to Eva's innocence, and also that he might realise that she is a woman he can exploit because of her ignorance
