In some circumstances, readers need to be able to evaluate an author's work for originality or contribution to the state of the art. If paraphrased or word-for-word ideas aren't quoted, the reader doesn't know if the line of argument is 1% new or 100% new.
Plagiarism—in a context where someone's work is being evaluated (generally, in academia or non-fiction publishing)—is a deliberate confusion of who contributed what to the argument being made. Which matters for evaluation of rationally presented ideas, to understand where arguments are coming from so criticism of those ideas can be located more easily.
If the thesis is taken from someone else, that's a gross abuse of academic standards. If you want to defend someone else's thesis on different grounds than they defended it, you can do so, but it should be made explicit that that's what you're doing, which entails citing the source of the thesis in some explicit way.
Furthermore, by citing sources, if a reader appreciates one line of thought but not what's built around it, they can go to that other source or author and start down a different path. Failing to cite sources makes that more difficult. IF it's recognized as most likely a quote, and IF the original source has high pagerank, it's easy to find. If not, you have to go consult academics in the area in question to see if they recognize it, or query the author to do what he or she should have done in the first place: cite the source.
I don't view it as theft, or anything like that. More like abuse or a waste of the reader's time and intellectual effort in trying to evaluate a complex argument without hints about the geneology of the component ideas.
In some circumstances, readers need to be able to evaluate an author's work for originality or contribution to the state of the art. If paraphrased or word-for-word ideas aren't quoted, the reader doesn't know if the line of argument is 1% new or 100% new.
Plagiarism—in a context where someone's work is being evaluated (generally, in academia or non-fiction publishing)—is a deliberate confusion of who contributed what to the argument being made. Which matters for evaluation of rationally presented ideas, to understand where arguments are coming from so criticism of those ideas can be located more easily.
If the thesis is taken from someone else, that's a gross abuse of academic standards. If you want to defend someone else's thesis on different grounds than they defended it, you can do so, but it should be made explicit that that's what you're doing, which entails citing the source of the thesis in some explicit way.
Furthermore, by citing sources, if a reader appreciates one line of thought but not what's built around it, they can go to that other source or author and start down a different path. Failing to cite sources makes that more difficult. IF it's recognized as most likely a quote, and IF the original source has high pagerank, it's easy to find. If not, you have to go consult academics in the area in question to see if they recognize it, or query the author to do what he or she should have done in the first place: cite the source.
I don't view it as theft, or anything like that. More like abuse or a waste of the reader's time and intellectual effort in trying to evaluate a complex argument without hints about the geneology of the component ideas.