在科學哲學中，指的是普遍性的陳述，此一陳述對自然事件的過程，加以描述並且解釋、或着在描述與解釋擇其一（比如説牛頓運動定律）；在法理學和政治哲學中，這是指共通於全部人類的權利與正義的體系，此一體系是從自然，而非社會的規則，或實證法中，所推衍出來。這個概念能夠追溯到亞里斯多德，他認為，「自然上是正當的」並不總是都等同於「法律上是正當的」。斯多噶派（參閲Stoicism）、西塞羅、羅馬法的法學者、聖保羅、聖奧古斯丁、格拉提安、聖托馬斯.阿奎那、鄧斯.司各脱、奧坎和蘇亞雷斯等人，也都以某種形式主張自然法則的存在。在現代時期，格勞秀斯和霍布斯則從「自然狀態」（state of nature）加以演繹，構告出自然法的體系，而繼之以社會契約論。洛克則將自然狀態描述為社會奠基於自然法的狀態。盧梭則假定，孤立的野蠻人善良有德，並且受到生物自我保存之本能與同情心的激勵。「獨立宣言」則在引用平等以及其他「不可讓度的」權利為「不證自明」之前，只簡短述及「自然的律則」。法國的「人權和公民權利宣言」則主張，自由、財產權、安全以及對抗壓迫，是「法令所不能更動的自然權利」。
natural law
In philosophy of science, a universal statement that describes and/or explains the course of natural events (e.g., Newton's laws of motion); in jurisprudence and political philosophy, a system of right or justice common to all humankind and derived from nature rather than from the rules of society, or positive law. This concept can be traced back to Aristotle, who held that what was “just by nature” was not always the same as what was “just by law.” In one form or another, the existence of natural law was asserted by the Stoics (see Stoicism), Cicero, the Roman jurists, St. Paul, St. Augustine, Gratian, Thomas Aquinas, John Duns Scotus, William of Ockham, and Francisco Suarez. In the modern period, Hugo Grotius and Thomas Hobbes constructed a system of natural law by deduction from a “state of nature” followed by a social contract. John Locke described the state of nature as a state of society based on natural law. J.-J. Rousseau postulated a savage who was virtuous in isolation and actuated by self-preservation and compassion. The Declaration of Independence refers only briefly to “the Laws of Nature” before citing equality and other “unalienable” rights as “self-evident.” The French Declaration of the Rights of Man and of the Citizen asserts liberty, property, security, and resistance to oppression as “imprescriptible natural rights.”.
