>>1798
You don't need to worry. Copyright is not relevant after (I believe) 100 years since the death of the author have passed. A lot of important philosophers are ripe for the picking - only most of them already have entire fields of study dedicated to their criticism and improvement.
>>1802
>by making a critique, im ipso facto proposing new ideas
No you aren't. You are merely advising against an already existing idea. That does not a new proposal make.