difficult sentence

[adel87]

dear all in this sentences
1)If I could just let her out at night

why they don't use i can ,what is the difference between could and can
2)Harry tried to argue back
what is the meaning of argue back
thank you

[Trance Freak]

dear all in this sentences
1)If I could just let her out at night

why they don't use i can ,what is the difference between could and can
2)Harry tried to argue back
what is the meaning of argue back
thank you

1-Could = unreal past, since you can't let her out. (you have your reasons)

2-to argue back:
as in arguing & arguing back
I offend you & you reply to my offence.
I say something & you say another.
--> always having something to say.