I'm just wondering what people think about this. I've had several literature classes where I'm assigned to analyze symbolism/figurative speech/other devices or themes and I almost always search online several analyses of the poem or story beforehand as a way of kick-starting my thinking process. However, I'm not entirely sure if this qualifies as plagiarism since many literary devices seem to be factual with not much room for opinion. I never copy the author's exact idea word-for-word, but my arguments seem to go down the same vein as what I've read because I can't help but be influenced.
It might be plagiarism or not, depending on how you present it. If you do it in such a way that the ideas seem to the reader to be yours alone, then it is clearly plagiarism. It isn't the "word-for-word" issue at all. That is irrelevant.
But if you quote the original work and then take off from there, extending the ideas of the others(s) and you provide a citation for it then it is clearly not plagiarism. Plagiarism is taking the ideas of another as if they were your own without attribution. It is always fine to extend the ideas of others, provided that it is clear that it is an extension and clear that you don't attribute the underlying ideas to yourself.
Don't confuse this with copyright, which is more to do with the actual words used.
However, if this is for a class, then the standards set by the professor may go beyond mere avoidance of plagiarism. So, while you may avoid plagiarism by using proper citation it isn't necessarily true that you meet the course standards. The judgement on that will only come from the instructor.