From Loux's: Metaphysics: A Contemporary Introduction.

The metaphysical theories of the rationalists, by contrast, were anything but conservative. In their hands, metaphysics results in abstract speculative systems far removed from any recognizably commonsense picture of the world. Here, one has only to skim the works of a thinker like Spinoza or Leibniz to appreciate the extravagance of rationalist metaphysics.

I'm still in the beginning of the book and I've read this in the introduction, so what's so speculative in rationalists metaphysics?


Speculation is used differently from the everyday use in philosophy. See a wiktionary definition:

speculative Philosophy: Philosophy, especially traditional metaphysical philosophy, which makes claims that cannot be verified by everyday experience of the physical world or by a scientific method.

I suppose that already answers your question. It's no opinion the author has, it's an obvious truth that the metaphysical systems of rationalists like Spinoza can't ever be proven to be true and that therefore they're highly speculative. There can be no method of proving that "everything is in God" - you can't prove it because you're inside the system you're making that claim about, there is no outside perspective. You can always (?) refute the premises of the speculative theory, or you can try to show that it's logically inconsistent, but you can neither prove nor disprove its contents.

Kant is no rationalist metaphysician, but his theoretical thinking is speculative in the same way (he calls it speculative philosophy himself). As a counterexample, consider Marx - everything he said about the development of history could be disproved post hoc (or maybe not, because you can always claim that this particular event did not conclude the development, I am not sure if this is such a good argument after all...). Some parts of language philosophy might be refuted by cognitive sciences; the "old" natural philosophy has long been proven to be false by physics.

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    Some of what 'speculative' indicates here may be denoting the scope of the metaphyiscal inquiry/method -- for Spinoza, the geometrical method of the Ethics permits an analysis of everything from cosmology and politics to psychology and morality. – Joseph Weissman Apr 14 '13 at 14:02
  • I agree that the rationalist metaphysics of Spinoza can't be proven to be true, and that this is obvious, and must have been obvious to Spinoza. He's then obviously doing something else entirely in his Ethics, although he starts of conventionally (for the time) enunciating a proof of God or his Nature according to his system. – Mozibur Ullah Apr 16 '13 at 16:24

Speculation is an important part of all thinking. Its one of the key process by which thought moves forward. Its as much a part of rational thinking as mythological or theological. It happens when thought reaches the limits of what is conventional for its time.

Here, one has only to skim the works of a thinker like Spinoza or Leibniz to appreciate the extravagance of rationalist metaphysics.

The current dominant paradigm for the modern intellect is scientific & mathematical. One has only to leaf through the books of Grothendieck to see just how baroque the constructions of a small sub-discipline (Algebraic Geometry) can become, initially it was laughed off as abstract nonsense, which is richly ironic as mathematics itself is seen to be itself far removed from the real world by the layman.

Similar things can be said for String Theory. Here the speculation is that atoms are not extensionless points but actually have extension. But note it was never proved that points were extensionless. It was a speculation that became a fact - until means and desires were seen useful in moving away from this position.

The key point about Christian Rationalist Metaphysics is simply they took God for granted. This is similar to Rationalist Islamic Theology - Kalam - which also took Allah as granted.


In aphorism 42 of Minima Moralia, Adorno writes that

Freedom of thought. – The suppression of philosophy by science has led, as is commonly known, to a separation of the two elements whose unity, according to Hegel, comprises the life of philosophy: reflection and speculation... Speculation is hit hard from the outset by the separation from reflection. It either degrades into the compliant parroting of traditional philosophical schemes or degenerates, in its distance from facts which have been rendered blind, into the babble of a non-binding private world view.

i.e. speculation these days is either a repetition of convention or a circumvention of the facts.

In this aphorism he then says that speculation also now appears (deformed) in the sciences, e.g. psychoanalytic free association, in which the patient is absolved of the need to labour on (think through) his thoughts.

This page says that speculation is the process whereby contradictions, revealed via dialectics, are resolved into higher unities.

Clearly, Adorno thought that there was a telling need for this speculation to be negative, which would do justice to Marx's (since crippled) judgment that philosophy had only interpreted the world. You can see that in the intro of Negative Dialectics

Speculative Moment 27-29. Even after renouncing idealism, it [philosophy] cannot dispense with speculation, albeit in a wider sense than Hegel’s all too positive one... Positivists are quick to write off Marxist materialism, which is one of objective laws of essence, which by no means proceed from immediate data or sets of axioms, as speculation.

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