Interest Is the Payment Made for the Use of Someone Else's Property, i.e., Someone Else's Purchasing Power

Those who provide finance to others do so to earn interest, which is the name given to the payments made in exchange for the purchasing power that has been made available by others. There is a vast economic literature on the reason that interest is actually paid but here I will only provide the most basic. Interest is the payment made for the use of part of someone else's property--in this case someone else's purchasing power--and can thus be seen as a form of rental. One lends out one's ability to buy at the present time in the same way as one might rent out one's house. At the end of the rental period, the aim is to have the full amount lent out returned, in the same way that one intends to reclaim one's house when the tenant moves out.

--Steven Kates, Free Market Economics: An Introduction for the General Reader, 3rd ed. (Cheltenham, UK: Edward Elgar Publishing, 2017), Kobo e-book.