Cicero went on to explain natural law as something that can contribute to the common good of society, while positive law would contribute to the security of society. Many contributions to natural law theory continued to be made, such as during the Renaissance and the Enlightenment. This led to the creation of more modern theories of natural law, combining natural law with other philosophical theories such as social contract theory. The important task is therefore to identify the ways in which an action itself may be imperfect. Thomas Aquinas obviously does not identify a master principle that can be used to determine whether an action is inherently flawed (although in an attempt to identify such a master principle in the work of Thomas Aquinas, Finnis 1998, pp. 126), although it indicates where to look – we must examine the characteristics that divide actions, such as their objects (ST IaIIae 18:2), their objectives (ST IaIIae 18:3), their circumstances (ST IaIIae 18:4), etc. An action can be distorted by a discrepancy between object and end – that is, between the immediate purpose of the action and its furthest point. For example, if one were to regulate one`s pursuit of a greater good in light of a lesser good—for example, if one sought friendship with God for mere physical survival and not the other way around—this would be considered an unreasonable act. An action can be vitiated by circumstances: while one is obliged to profess one`s faith in God, there are certain circumstances in which it is inappropriate to do so (ST. IIaIIae 3:2). An action can be vitiated by its intention alone: to be directed against property – as in murder (ST IIaIIae 64:6), lying (ST IIaIIae 110:3) and blasphemy (ST IIaIIae 13:2) – always means acting inappropriately.
Thomas Aquinas has no illusions that we will be able to establish principles of conduct that comprehensively determine the right behavior, as if for every situation in which a good choice must be made, there is a rule that covers the situation. It allows the Aristotelian to understand that the details of the situation always go beyond his own rules, so that one always needs moral and intellectual virtues to act well (commentary NE, II, 2, 259). But he denies that this means that there are no principles of good conduct that apply everywhere and always, and some even absolutely. According to Thomas Aquinas, killing innocent people is always wrong, as is lying, adultery, bestiality and blasphemy; And whether they are always wrong is a matter of natural law. (These are just examples, not an exhaustive list of absolutely prohibited acts.) While we will focus primarily on the status of natural law as principles of practical rationality, we should consider, at least for a moment, the significance of the claim that natural law is an aspect of divine providence. The basic thesis confirmed here by Thomas Aquinas is that the natural law is a participation in the eternal law (St. IaIIae 91:2). For Thomas Aquinas, the eternal law is the rational plan by which all creation is ordered (ST IaIIae 91:1); Natural law is man`s “partake” of the eternal law (ST IaIIae 91:2). While non-rational beings have a share in the eternal law only when they are ordained by it—their actions are freely derived from their definite nature, the existence of which flows from God`s will in accordance with God`s eternal plan—rational beings like us are able to grasp our part of the eternal law and act freely accordingly (ST IaIIae 91, 2) It is this characteristic of natural law that, according to Thomas Aquinas, justifies calling natural law “law”. For the law, as defined by Thomas Aquinas (ST IaIIae 90:4), is a rule of action established by one who cares for the community; and since God cares about the whole universe, God`s decision to give birth to beings who can act freely and in accordance with the principles of reason is sufficient to justify our thinking of these principles of reason as law.
It is essential to the position of natural law that there be things that are universal and naturally good. But how is universal and natural goodness possible? Given the variability of human tastes and desires, how can there be such universal goods? The separability thesis, at the most general level, simply denies the overlapping naturalism thesis; According to the separability thesis, there is no conceptual overlap between the concepts of law and morality.