Naturalism is divided into two philosophical stances: * Naturalized epistemology (or Methodological naturalism or scientific naturalism) which focuses on epistemology: This stance is concerned with knowledge: what are methods for gaining trustworthy knowledge of the natural world? It is an epistemological view that is specifically concerned with practical methods for acquiring knowledge, irrespective of one's metaphysical or religious views. It requires that hypotheses be explained and tested only by reference to natural causes and events. Explanations of observable effects are considered to be practical and useful only when they hypothesize natural causes (i.e., specific mechanisms, not indeterminate miracles). Methodological naturalism is the principle underlying all of modern science.