Hulsmann’s piece was excellent, especially the review/intro part. Do you have a link (pdf?) for Bob Murphy’s angle?
A common thread in all theories of interest seems to be the sooner/later, cause/effect, means/end paradigms, which are merely different aspects of one and same thing: before/after location on the time axis. My (layman) intuition on the source of interest comes from experience and also involves time but from an uncertainty, opportunity angle. Having control over $100 now is always preferable to having such control a year from now because my freedom to use (control, allocate, invest, etc.) the $100 in combination with the opportunities that may come my way over that year is always worth a non-zero amount to me. There’s a saying that: “Success is when opportunity meets preparation.” My control over the $100 (vs lacking it) is an essential part of the “preparation”. If the opportunity came, and I didn’t have the $100, the opportunity is lost.
In this light, to me, interest is inextricably related to opportunity cost. When you ask me to lend you $100 for a year, I will price the loan (interest) to match (or exceed) my perception of potential opportunity lost (in addition to pricing in your credit risk, of course). The more volatile the environment (markets), the larger the number and intensity of potential opportunities over the year (distressed sellers of goods/assets, IBM shares drop 50%, etc.) and/or the higher the probability I’ll need them to cover my own potential losses/risks, hence the costlier the loan. The longer the period I’m denied my control over the $100, the larger the number of opportunities potentially missed (or potential losses/risks), the larger the uncertainty span of all possible outcomes that may affect me (positively or negatively) hence the larger amount of total interest I would demand in proportion to the length of the loan. These uncertainty forces are considered when pricing bonds and are reflected in the shapes of the bond yield curves (typically, higher annual yields for longer maturities, all other things being equal.)
Z.