Plagiarism and professionalism are opposites. A professional’s status depends on reputation. A professional might say,
| If you use and cite my work, you enhance my reputation. |
| If you use it but don’t cite it, you don’t. That’s plagiarism. |
Moreover, you endanger your status. Your potential clients or readers or students may find out that your reputation is partly false.
Information and text processing systems make it easy to find others’ work and misrepresent it as your own. So the social penalty for this sin must be severe. A professional who commits it and is discovered suffers disgrace and perhaps a career downturn. To guide students preparing to be professionals, academic penalties are proportional. But disgrace doesn’t really come in small doses.
Professionals police themselves. Scientists use the referee system to ensure integrity of research results; this also helps insure integrity of authorship.
Police yourself. Cite the source of every fact or conclusion that you include in a paper, unless it’s your own deduction or common knowledge to someone with a background similar to your targeted reader’s. When you're not sure about common knowledge, ask. Your reader must be able to backtrack your work, and you owe credit to your sources.
Failure to give credit is a far greater sin than mathematical error.