Quite frankly I am surprised this topic got approved.
If you don't know the arguments put forward for the multiple athorship of Isiah you should ask. Or you should find out what they are from other sources (ideally the critics themselves) and address their real arguments.
When you come up with an intelligent post on the subject maybe you'll get intelligent responses. As initiator of the thread you set the tone, and it is incumbent on you to find something worth saying.