any theory which holds that beliefs are justified, or can be held as true, if they are based on foundation beliefs, such as a self-evident truth, or a basic proposition which is self-justifying. An example is the work of Rene Descartes (1596-1650) which identifies 'cogito ergo sum' - 'I think, therefore I am' - as a foundation belief. Many critics dispute that such foundations - absolutely free of doubt or scepticism - can be found