看一本语法书上介绍He has no house in which to live是对的,然介词in放后面
He has no house which to live in却不对,为什么不对?
答：这个问题不错!不太好回答.光说习惯是不能服人的.
首先,我们知道,He has no house 后面跟的是一个定语.
用定语从句：
He has no house where he can live.
He has no house in which he can live.
He has no house which he can live in.
这三种说法都是正确的.
其次我们知道,英语中有疑问不定式：wh-词+不定式,可以作宾语,相当于一个宾语从句,如：
I don't know what to do.=I don't know what I should do.我不知道该做什么.
I don't know where to live.=I don't know where I should live.我不知道该住哪里.
同时,我们也见过一种介词+which +不定式的“特殊不定式”可以作定语,相当于一个定语从句的用法,这样的考题也是有的：
Now I’ll present the facts ____C______.
A.on which to be based my opinion B.which to base my opinion on
C.upon which to base my opinion D.which to base my opinion upon
We need more actual facts on which to base our arguments
=We need more actual facts on which we can base our arguments
至于这个相当于一个定语从句的作后置定语的“特殊不定式”为什么可以用介词+which +不定式,而不用which+不定式+介词,除了习惯（我们没有见到别人这么用过）以外,也可以去理
in which =where,in which to live =where to live,这是大家熟悉的一种疑问不定式的变体.
用了介词+which后,大家知道之间的关系,用不定式是偷懒,从定语从句变过来的.
但用了which之后,大家一方面不能马上知道两者之间的关系,一方面会以为后面的应该是一个定语从句（结果不是）.至于which he can live in 这个定语从句,为什么不能简化为whcih to live in,就说不清楚了.
只能说：因为大家都不这么说,所以不能这么说.