The background to the interest in metaphysics of the Spanish Jesuit Francisco Suárez (1547–1617) was the contemporary rejection of metaphysics as a basis for theological thinking.
Due to the 16th. century Protestant Reformation the primacy of metaphysical thinking was being questioned. Luther had already banned some works by Plato and Aristotle as errors and sins, among them Metaphysics. His reasoning was that, because of original sin, humans could no longer achieve understanding of truth through logic. This meant that the only viable path to truth was the scriptures, not philosophical theology.
Renaissance humanists also had had reservations about metaphysical thinking. Humanism believed in a natural metaphysics which considered the supernatural as a myth and Nature as the only being. It rejected belief without a reasoned base and the divine revelation of truth. It was championed in Europe by Petrarch, Erasmus, More, Rabelais and Pico della Mirandola.
Contrary to these anti-metaphysical movements, Suárez wrote his Metaphysical Disputations asserting the legitimacy and importance of a renewed metaphysical basis for theology.
Disputationes Metaphysicae (1597) is based on Aristotle and Aquinas and includes concepts from Duns Scotus and Luis de Molina. It is sufficiently original compared to Aquinas' systemisation that it earned the name Suárezianism. It consists of fifty-four disputations which systemise all aristotelian metaphysics. It was used for more than a century as a textbook at most European universities, both Catholic and Protestant.
The work is divided into two tomes. The first deals with the properties and causes of being. The second is a metaphysical examination of items beneath being.
Tome 1 analyses the concept of being as existence, inclusive of all types of being. He then turns to the essential properties of being: unity, truth, goodness. In unity he discusses individuation, universal natures and distinctions. Under truth, falsity is discussed and under goodness, evil. Next he considers the causes of being in general and by types. To conclude tome 1 he compares causes and effects and how causes are interrelated.
Tome 2 analyses being into infinite and finite. The infinite being is God whose existence and unicity are demonstrated metaphysically. It continues with an investigation through human reason of the divinity. He then turns to the finite being where he denies the distinction between essence and existence in creatures. He also looks at the differences between substance and accident. The 54th. disputation discusses the beings of reason: negation, privations and relations dependent on reason, which are not included in metaphysics.
Suárez believes in a trinitarian God who is creator and sustainer of humans and their world. God's existence is necessary and the infinite divinity is eternal and immutable. Suárez's God is good and omniscient and organises the world in a providential fashion. However, because of sin, humans need God's grace to achieve their salvation. This has been prepared for by the Incarnation.
From aristotelian thought Suárez inherited the concept that objects are made up of matter and form. He also accepted the four causes explanation: material, formal, efficient, and final. These give answers to the questions of material changes in substances. He embraces Aristotle's categorical organisation of substance and nine categories of accidents. He adopted the ideas that the human soul takes the form of the body and, in ethics, the language of final ends, happiness and virtue.
The author's definition of the object of metaphysics includes both finite and infinite beings with their substances and accidents. It excludes reasoned beings which are only objects of thought.
The function of metaphysics is to classify the properties of being through its principles and causes. The properties, for Suárez, are the characteristics which the members all possess, yet are not essential. The ability to laugh is an example.
For internal reasons of his Jesuit order which required adherence to Aristotle in philosophy and Aquinas in theology, Suárez probably exaggerated his faithfulness to Aquinas.
As the basis for conceiving the natural law Suárez put more emphasis on God's command than Aquinas. He also replaced Aquinas' focus on good and bad by prioritising right and wrong. However he did uphold Aquinas' core teachings on natural law.
Aquinas wrote tacitly on defensive and offensive war. However Suárez insisted more on the ethical importance of this distinction. He suggests that force used defensively aims to prevent a wrongdoing. In contrast offensive use of force is directed at satisfaction for harm already inflicted.
Both Suárez and Scotus have a similar problem: to build a metaphysics and theology which correspond to aristotelian science. Within this context the concept 'being' needs to have enough unity to serve as a middle term between both, in order to provide scientific knowledge of God's existence and characteristics. Being fits this requirement as it covers finite and infinite existence.
Luis de Molina
Molina analysed the problem of the doctrinal contradiction between grace and free will. He resolved that God possesses a middle knowledge which can predict human behaviours, without falling into determinism. In contrast Aquinas argued that God predetermines human will to act freely. Molina thought that this view included a hidden determinism.
Aquinas taught that God's knowledge was double: cognition of past, present and future existences; knowledge of past, present and future possible existences. Molina argued for a middle knowledge which is of future conditional events. This implies that the divinity knows human reaction if grace is offered and so decrees the circumstances and grace necessary to ensure human cooperation.
Debate between the opposing interpretations went on for three centuries and the Church resolved in Molina's favour. Suárez adopted Molina's viewpoint and spread it to both Catholic and Protestant universities.