Answer:
Plagiarism is a form of literary fraud in which a writer passes arguments, claims, and findings made by other researchers as his or her own without giving due credit to the original authors of those arguments, etc.
The paragraph above, if graded, could have points deducted because it is making claims that are clearly historical arguments and findings made by others, but the writer of the paragraph does not cite the sources in any formal or informal way, which is what constitutes plagiarism.