Originally Posted by Jozawun
I am interested in pdurrant's view that it would be ethical to copy the book if you purchased it, but not if you borrowed it from a library.
What is the ethical difference, given that you have actually paid for it in both cases?
In the first one has paid for permanent access to a copy of the work. Making an additional copy of the work for one's own use seems plainly ethical to me, and is legal in the US, although not in the UK.
In the second case, one has paid (through taxes) for communal, temporary access to a limited number of copies of the work. Making an additional copy of the work to gain permanent access to a copy of the work without further compensating the author is unethical.
If everyone did the first, no-one would suffer any loss of revenue. If everyone did the second, there would be a large enough loss of revenue that it would no longer be economically viable to make books available to libraries.