Pre-Socratic metaphysics in Greece
Rejecting mythological and divine explanations, he sought a single first cause or Arche (origin or beginning) under which all phenomena could be explained, and concluded that this first cause was in fact moisture or water.
Thales also taught that the world is harmonious, has a harmonious structure, and thus is intelligible to rational understanding.
Methodologically, the Eleatics were broadly rationalist, and took logical standards of clarity and necessity to be the criteria of truth.
Parmenides’ chief doctrine was that reality is a single unchanging and universal Being.
His philosophy, expressed in brief aphorisms, is quite cryptic.
For instance, he also taught the unity of opposites.
They are considered forerunners of the scientific method.
Socrates and Plato
Platonic realism (also considered a form of idealism) is considered to be a solution to the problem of universals; i.e., what particular objects have in common is that they share a specific Form which is universal to all others of their respective kind.
The theory has a number of other aspects:
- Epistemological: knowledge of the Forms is more certain than mere sensory data.
- Ethical: The Form of the Good sets an objective standard for morality.
- Time and Change: The world of the Forms is eternal and unchanging. Time and change belong only to the lower sensory world. “Time is a moving image of Eternity”.
- Abstract objects and mathematics: Numbers, geometrical figures, etc., exist mind-independently in the World of Forms.
Platonism developed into Neoplatonism, a philosophy with a monotheistic and mystical flavour that survived well into the early Christian era.
His solution to the problem of universals contrasts with Plato’s.
Whereas Platonic Forms exist in a separate realm, and can exist uninstantiated in visible things, Aristotelean essences “indwell” in particulars.
The Aristotelean theory of change and causality stretches to four causes: the material, formal, efficient and final.
The efficient cause corresponds to what is now known as a cause simpliciter.
Final causes are explicitly teleological, a concept now regarded as controversial in science.
The Matter/Form dichotomy was to become highly influential in later philosophy as the substance/essence distinction.
Scholasticism and the Middle Ages
Scholastic philosophy took place within an established framework blending Christian theology with Aristotelean teachings.
Although fundamental orthodoxies could not be challenged, there were nonetheless deep metaphysical disagreements, particularly over the problem of universals, which engaged Duns Scotus and Pierre Abelard. William of Ockham is remembered for his principle of ontological parsimony.
In the early modern period (17th and 18th centuries), the system-building scope of philosophy is often linked to the rationalist method of philosophy, that is the technique of deducing the nature of the world by pure reason.
The scholastic concepts of substance and accident were employed.
- Leibniz proposed in his Monadology a plurality of non-interacting substances.
- Descartes is famous for his Dualism of material and mental substances.
- Spinoza believed reality was a single substance of God-or-nature.
British empiricism marked something of a reaction to rationalist and system-building philosophy, or speculative metaphysics as it was pejoratively termed.
The sceptic David Hume famously declared that most metaphysics should be consigned to the flames (see below).
Hume was notorious among his contemporaries as one of the first philosophers to openly doubt religion, but is better known now for his critique of causality.
Other philosophers, notably George Berkeley were led from empiricism to idealistic metaphysics.
Immanuel Kant attempted a grand synthesis and revision of the trends already mentioned: scholastic philosophy, systematic metaphysics, and skeptical empiricism, not to forget the burgeoning science of his day.
Like the systems builders, he had an overarching framework in which all questions were to be addressed.
Like Hume, who famously woke him from his ‘dogmatic slumbers’, he was suspicious of metaphysical speculation, and also places much emphasis on the limitations of the human mind.
Kant saw rationalist philosophers as aiming for a kind of metaphysical knowledge he defined as the synthetic apriori — that is knowledge that does not come from the senses (it is a priori) but is nonetheless about reality (synthetic).
Inasmuch as it is about reality, it is unlike abstract mathematical propositions (which he terms analytical apriori), and being apriori it is distinct from empirical, scientific knowledge (which he terms synthetic aposteriori).
The only synthetic apriori knowledge we can have is of how our minds organise the data of the senses; that organising framework is space and time, which for Kant have no mind-independent existence, but nonetheless operate uniformly in all humans.
Apriori knowledge of space and time is all that remains of metaphysics as traditionally conceived.
There is a reality beyond sensory data or phenomena, which he calls the realm of noumena; however, we cannot know it as it is in itself, but only as it appears to us.
He allows himself to speculate that the origins of God, morality, and free will might exist in the noumenal realm, but these possibilities have to be set against its basic unknowability for humans.
Although he saw himself as having disposed of metaphysics, in a sense, he has generally been regarded in retrospect, as having a metaphysics of his own.
19th Century philosophy was overwhelmingly influenced by Kant and his successors. Schopenhauer, Schelling, Fichte and Hegel all purveyed their own panoramic versions of German Idealism, Kant’s own caution about metaphysical speculation, and refutation of idealism, having fallen by the wayside. The idealistic impulse continued into the early 20th century with British idealists such as F. H. Bradley and J. M. E. McTaggart.
Early analytical philosophy and positivism
During the period when idealism was dominant in philosophy, science had been making great advances.
The arrival of a new generation of scientifically minded philosophers led to a sharp decline in the popularity of idealism during the 1920s.
The early to mid 20th century philosophy also saw a trend to reject metaphysical questions as meaningless.
At around the same time, the American pragmatists were steering a middle course between materialism and idealism.
The forces that shaped analytical philosophy — the break with idealism, and the influence of science — were much less significant outside the English speaking world, although there was a shared turn toward language.
Continental philosophy continued in a trajectory from post Kantianism.
The phenomenology of Husserl and others was intended as a collaborative project for the investigation of the features and structure of consciousness common to all humans, in line with Kant’s basing his synthetic apriori on the uniform operation of consciousness.
It was officially neutral with regards to ontology, but was nonetheless to spawn a number of metaphysical systems.
The speculative realism movement marks a return to full blooded realism.
Later analytical philosophy
While early analytic philosophy tended to reject metaphysical theorizing, under the influence of logical positivism, it was revived in the second half of the twentieth century.
However, the focus of analytical philosophy is generally away from the construction of all-encompassing systems and towards close analysis of individual ideas.
Among the developments that led to the revival of metaphysical theorizing were Quine’s attack on the analytic-synthetic distinction, which was generally taken to undermine Carnap’s distinction between existence questions internal to a framework and those external to it.
The philosophy of fiction, the problem of empty names, and the debate over existence’s status as a property have all risen out of relative obscurity to become central concerns, while perennial issues such as free will, possible worlds, and the philosophy of time have had new life breathed into them.