You are striving for a close, in-depth analysis which relates significantly to the work as a whole, but which is limited to only one or two aspects of the work. Attempts to pass off others' ideas as your own are more transparent than you might suspect. These papers should demonstrate the thought you have given to the work. A paper that merely repeats or paraphrases others' words or ideas is not a critical essay. You need not use external sources, but if you do, you must document any ideas gleaned from them in your essay.
Plagiarism is unacceptable , even if unintentional.