In writing about a philosophical problem, it is often good to discuss and make reference to the work of others. Often it is necessary to recount the arguments or positions of others. Sometimes it is necessary to quote others verbatim—for example in order to provide evidence that some philosopher makes a certain claim, it may be desirable to cite his or her words. However, it must at all times be clear which are the claims attributed to others, and which are the claims made by the author him or herself. Moreover, it must be indicated clearly when the exact words of others are being reproduced, providing a page reference and the bibliographical details of the work being cited. Failing to do so may amount to plagiarism. Your work might be marked down or even failed if your sources are not acknowledged properly.
Plagiarism is often defined as follows: using the words or ideas of others without proper acknowledgement of the source. The dividing line between plagiarism and proper acknowledgement of sources is fine, but usually quite clear.
For example, consider the short passage which might occur in an essay in Figure 1 and the modified version in Figure 2:
Perry argues "that the essential indexical poses a problem for various otherwise plausible accounts of belief" (Perry 1979, p. 3). The first account he considers is the view he calls "the doctrine of propositions", the second …
In "The Essential Indexical", Perry argues that the essential indexical poses a problem for various otherwise plausible accounts of belief. The first account he considers is the view he calls "the doctrine of propositions", the second …
As innocent as this modification may seem, the second version does in fact involve plagiarism as defined above: the exact words of Perry are used without properly acknowledging the source. It is therefore crucial that, in writing essays, you indicate clearly, at all times, whether you are speaking with your own voice or quoting someone else. Failure to do so may not only cause misunderstandings, but could even be interpreted as an attempt to cheat. It is therefore important to be quite conscientious about proper acknowledgement when quoting verbatim.
It is also important to acknowledge properly your sources when you are not quoting directly, i.e. when you are merely paraphrasing. If you take ideas and arguments from others it is important that you say so explicitly.
Essays involving plagiarism (the unacknowledged use of the work of others—their words or their ideas) will be marked down. In some cases this may be exclusively a presentational problem, but this is one of the criteria by which you are marked, and it is an important criterion, especially when your failure to acknowledge misleads the reader. In other cases, it may in addition mean that your essay is extremely derivative and—instead of answering the philosophical question your essay is supposed to answer—merely reports what someone else says about this question.
Finally the severest cases: an unacknowledged use of another’s work in an attempt to deceive the reader is a form of cheating: cheating yourself and cheating the person marking your essay. In the most severe cases, essays may be disqualified.