The Use of Basic Science

Anecdotal evidence strongly suggests that basic, or curiosity driven, research easily pays for itself.  This is confirmed by quantitative estimates of the return on investment.  But in this case: Why should the tax payer – rather than private investors – pay?  Should the tax payer also support applied, or mission oriented, research?  Can we anticipate returns from discoveries in fields such as cosmology and particle physics, which study systems that are remote from everyday life?  If not, how much importance should we give to the cultural value of such work, and to the value of spin-offs that it may generate?