What is the difference between 行くなら and 行けば


> シカゴへ行く(の)ならバスで行ったらどうですか

What is the difference between 行く(の)なら and 行けば?




Generally speaking,

> Correct Japanese: （もし）行く（の）なら  
>  Correct Japanese: （もし）行けば  
>  Correct Japanese: （もし）行くのであれば

The above short usages are right. However,

> Correct Japanese: （もし）シカゴへ行く（の）なら、バスで行ったらどうですか  
>  NOT Correct Japanese: （もし）シカゴへ行けば、バスで行ったらどうですか  
>  Correct Japanese: （もし）シカゴへ行くのであれば、バスで行ったらどうですか

Instead of the difference explanation, I'd like to show you the following
sample sentences. The following three sentences correspond to "If you follow
the instruction"

> Correct Japanese: （もし）命令に従う（の）なら, "You have not yet followed the
> instruction, but if you follow it in the future..."  
>  Correct Japanese: （もし）命令に従えば, "You don't follow the instruction, but once
> you follow it, then..."  
>  Correct Japanese: （もし）命令に従うのであれば, "You have not yet followed the
> instruction, but if you follow it in the future..."

The difference comes from the tense of the situation.

「シカゴへ行く（の）なら」 talks about the future, or you have not arrived at Chicago yet.

「（もし）シカゴへ行けば」 has the sense of complete tense. For example, "If you come to
Chicago in February 2017, you can meet Mr. Obama."

