Armstrong's view of knowledge is that the conditions of knowledge are satisfied when you have a justified true belief that you arrived at through a reliable process: that is, the belief was caused by some factor in the external world (hence the label of externalism). Armstrong uses the analogy of a thermometer: as a thermometer changes to reflect the temperature of the environment it is in, so must one's beliefs if they are reliably formed. The connection between knowledge and the external world, for Armstrong, is a nomological relationship (that is, a law of nature relationship). Here, Armstrong's view is broadly similar to that of Alvin Goldman and Robert Nozick. The intuitions that lead to this kind of externalism led Alvin Plantinga towards an account of knowledge that added the requirement for 'properly-functioning' cognitive systems operating according to a design plan.