Definition of 自然主義 Shizenshugi (Naturalism)

自然主義　
〔哲〕 存在や価値の根本に自然を考える立場の総称。一般に、超自然的なもの（理想・規範・超越者など）の独自性を認めず、自然的なもの（物質・感覚・衝動・生命など）を基盤にして物事をとらえる。
宗教上では、汎神(はんしん)論にほぼ同じ。
-excerpt from @nifty辞書

Naturalism
1. Action arising from or based on natural instincts and desires alone.
2.Philosophy.
a. the view of the world that takes account only of natural elements and forces, excluding the supernatural or spiritual.
b. the belief that all phenomena are covered by laws of science and that all teleological explanations are therefore without value.
-excerpt from http://dictionary.reference.com