In a sound currency world, interest rates are set by the relative availability of funds for investment - that is, they are counter-cyclically market-determined: if there is little investment, rates will be low, if the economy is booming, rates will naturally rise.
Secondly, the rate of deflation is determined by the rate of increase in the economy: if the economy is shrinking over time, there is no deflationary incentive to hold - so here again the currency is counter-cyclical, discouraging rapid growth while allowing for measured growth.
Is that sand? Or sanity?