When Werner Heisenberg presented his views of the fundamental indeterminism to which his uncertainty principle pointed in the basic levels of reality described by quantum mechanics, he used the Aristotelian technical terms of act and potency, affirming that the quantum system is in potency before the measurement and that the potency was actualised when the measurement took place, speaking thus of a ‘new ontology’ of quantum mechanics. I argue that Thomas Aquinas’ Aristotelian account of indeterminism in nature, through his analysis of the notions of matter as potency and form as act, can provide a suitable framework to understand Heisenberg's philosophical intuition about the nature of quantum systems.

Modern biologists often claim to be committed to a strong reductionist conception of scientific explanation, in contrast to the teleological explanations of medieval natural philosophers. Attention to the actual explanatory strategies used in contemporary biological research, however, reveals a dependence on final cause explanations. A good example can be found in adaptation studies where explanation is typically in terms of optimal design models. Such optimality models are teleological precisely in the way Thomas Aquinas and Albertus Magnus insisted explanation of natural forms must be. Consequently, the non-reductionist conception of final cause defended by Neo-Aristotelian philosophers of science is entirely consistent with common modes of explanation used by contemporary biological researchers.

In light of Aquinas's teaching, I first critique William Dembski's mathematical approach to design in nature, and then critique Michael Behe's failure to distinguish between causes that physically produce an object and causes responsible for the plan for that object. I then investigate Aquinas's Fifth Way, both comparing it to Paley's argument, and attempting to discern where it disagrees with atheistic accounts of evolution. I show that Aquinas acknowledges that living things can result from finality at one level and chance at another level; in other words, he acknowledges that contingent intermediary causes are able to be part of God's plan or design for the production of new species. Thus, the disagreement between Aquinas and the proponents of atheistic versions of evolution is not due to any denial on his part that chance may have role in the production of new species. I then show that even atheist biologists and philosophers recognize a regular tendency in nature to something good, namely, the tendency for niches to be filled, resulting in the good of biodiversity. Where they and Aquinas part ways is as to whether things that lack cognition can only tend to an end when directed by an intelligent being.

To develop a philosophical framework to address the specification of sex/gender in humans, I will begin by summarizing what we know about the biology of sex determination in human beings. Basically, sex/gender is specified by several networks of genes anchored in the genetic interaction between the two genes, Sry and Sox9. Next, I will propose that this biological mechanism is best understood within a philosophical anthropology that embraces insights taken from systems biology to articulate a hylomorphism that explains the integrity, dynamism, and teleology of the human organism. The systems perspective described here represents one attempt to reformulate the received philosophical framework of classical Aristotelian-Thomistic hylomorphism so that it incorporates the insights of modern biology. Finally, I will use the systems perspective and key principles articulated by St. Thomas Aquinas in his philosophy of nature to identify criteria that could be used to specify the sex/gender of a particular human being: The most certain criterion for maleness would be the capacity to produce sperm while the most certain criterion for femaleness would be the complementary capacity to produce eggs. Deviations from this criterion would decrease the certitude of our judgment regarding the sex/gender of the individual.

Why our interest in natural law still today? We can always criticize obligations and found human rights on the basis of natural law and we cannot accept a large gap between inclinations and desires on one hand and norms on the other. Natural law is not the lowest common denominator among men and is not always immediately apparent. We can find out it by a resolutio, going back from every day moral experience, from virtues and vices, from civil laws to the first principles. Natural law is the work of practical rationality, that makes order, looking with attention to reality and requires harmony between reason and inclinations towards perfect goods. Human desire is informed by reason and practical reason is always also speculative reason, because it knows reality. Desire “has eyes”, recognizing good. What goodness consists in is perfection. Since human being is open to infinity, the main and inclusive desire is desire for happiness and for God. Inclinations towards good are known, valued, interpreted by practical reason and they become moral norms thanks to the same practical reason.The normative dimension of law is also finalistic. The idea of conveniens is different from both Kantian and Utilitarian points of view. Ethical virtues are the flourishment of the seeds of natural law and there is no necessary opposition between freedom and natural law.

This article aims to demonstrate that Thomas Aquinas's metaphysics of being, in which evil is considered a privation or lack of perfection introduced only by the creature against God's intention, is a remarkable starting point for solving the main problems involved in the modern and contemporary debate on the problem of evil. It also seeks to prove that Aquinas's position is neither reducible to an ‘optimistic theodicy’ –such as Leibniz's theodicy– nor to a ‘free will defence’.