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He said it: Newton in Principia, on rules of reasoning for experimental philosophy

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The ongoing debates over methodological naturalism have pointed us back to Newton’s Rules for scientific reasoning. So, thanks to Paul Halshall of Fordham University’s Modern History Sourcebook, let us cite for reference:


>> Modern History Sourcebook:
Isaac Newton:
The Mathematical Principles of Natural Philosophy


[The Rules of Reasoning in Philosophy]


We are to admit no more causes of natural things, than such as are both true and sufficient to explain their appearances.

To this purpose the philosophers say, that Nature does nothing in vain, and more is in vain, when less will serve; for Nature is pleased with simplicity, and affects not the pomp of superfluous causes.


Therefore to the same natural effects we must, as far as possible, assign the same causes.

As to respiration in a man, and in a beast; the descent of stones in Europe and in America; the light of`our culinary fire and of the sun; the reflection of light in the earth, and in the planets


The qualities of bodies, which admit neither intension nor remission of degrees, and which are found to belong to all bodies within reach of our experiments, are to be esteemed the universal qualities of all bodies whatsoever.

For since the qualities of bodies are only known to us by experiments, we are to hold for universal, all such as universally agree with experiments; and such as are not liable to diminution, can never be quite taken away. We are certainly not to relinquish the evidence of experiments for the sake of dreams and vain fictions of our own devising; nor are we to recede from the analogy of Nature, which is wont to be simple, and always consonant to itself. We no other way know the extension of bodies, than by our senses, nor do these reach it in all bodies; but because we perceive extension in all that are sensible, therefore we ascribe it universally to all others, also. That abundance of bodies are hard we learn by experience. And because the hardness of the whole arises from the hardness of the parts, we therefore justly infer the hardness of the undivided particles not only of the bodies we feel but of all others. That all bodies are impenetrable we gather not from reason, but from sensation. The bodies which we handle we find impenetrables and thence conclude impenetrability to be a universal property of all bodies whatsoever. That all bodies are moveable, and endowed with certain powers (which we call the forces of inertia) or persevering in their motion or in their rest, we only infer from the like properties observed in the bodies which we have seen. The extension, hardness, impenetrability, mobility, and force of inertia of the whole result from the extension, hardness, impenetrability, mobility, and forces of inertia of the parts: and thence we conclude that the least particles of all bodies to be also all extended, and hard, and impenetrable, and moveable, and endowed with their proper forces of inertia. And this is the foundation of all philosophy. Moreover, that the divided but contiguous particles of bodies may be separated from one another, is a matter of observation; and, in the particles that remain undivided, our minds are able to distinguish yet lesser parts, as is mathematically demonstrated. But whether the parts so distinguished, and not yet divided, may, by the powers of nature, be actually divided and separated from one another, we cannot certainly determine. Yet had we the proof of but one experiment, that any undivided particle, in breaking a hard and solid body, suffered a division, we might by virtue of this rule, conclude, that the undivided as well as the divided particles, may be divided and actually separated into infinity.

Lastly, if it universally appears, by experiments and astronomical observations, that all bodies about the earth, gravitate toward the earth; and that in proportion to the quantity of matter which they severally contain; that the moon likewise, according to the quantity of its matter, gravitates toward the earth; that on the other hand our sea gravitates toward the moon; and all the planets mutually one toward another; and the comets in like manner towards the sun; we must, in consequence of this rule, universally allow, that all bodies whatsoever are endowed with a principle of mutual gravitation. For the argument from the appearances concludes with more force for the universal gravitation of all bodies, than for their impenetrability, of which among those in the celestial regions, we have no experiments, nor any manner of observation. Not that I affirm gravity to be essential to all bodies. By their inherent force I mean nothing but their force of` inertia. This is immutable. Their gravity is diminished as they recede from the earth.


In experimental philosophy we are to look upon propositions collected by general induction from phenomena as accurately or very nearly true, notwithstanding any contrary hypotheses that may be imagined, till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions.

This rule we must follow that the argument of induction may not be evaded by hypotheses.

Isaac Newton, The Mathematical Principles of Natural Philosophy, trans. A. Motte (London, 1729). [Capitalization and spelling have been modernized.] >>


We find here statements of principles of induction, generalisation and provisionality of inductive reasoning.  In particular, we see that inductive genralisations are extended from that which we may directly observe to those that are beyond our reach based on an informed principle of uniformity, and that his is subject to correction in light of experiments, not naked speculative principles.

The particular relevance of this to the debates over design is that we actually do have a well known widely tested and substantiated cause for functionally specific complex organisation and associated information: art, or design. It is known adequate, and it is in fact the known adequate cause, analysis and experience alike showing that the other source of high contingency is utterly inadequate: chance.

So, we have good inductive warrant for inferring from sign, FSCO/I to signified: intelligently directed contingency — aka, design, aka art — as credible causal mechanism. On the same uniformity principle championed by Newton and used by others following Lyell to extend to cases where due to remoteness in time, we may not observe the past of origins, but may infer about it on traces in the present.

Such inductive inferences are obviously provisional and subject to correction on further evidence, but that holds for all origins science investigations.

And of course, inductive genralisations cannot utterly forbid rare exceptions or circumstances where a hitherto well substantiated “law” of nature breaks down by failing to give good predictions. That is what happened with classical physics c 1880 – 1930, giving rise to the modern quantum and relativistic era in physics. Where also givne that most scientific paradigms have been superseded across time the pessimistic induction obtains: we have no grounds for imagining that we have arrived at final truth today.

Thus also, those who are fond of asserting that say Darwinian macro-evolution as the explanation for origin of body plan level biodiversity is a “fact” on the level of the theory of gravitation, are doubly in error. For, the Newtonian theory of gravitation has found a more advanced cousin, as an aspect of the General theory of Relativity. And, even if that had not happened, the logic of induction is inherently provisional.

Newton still has much to teach us about science. END

2 Replies to “He said it: Newton in Principia, on rules of reasoning for experimental philosophy

  1. 1
    Mytheos says:

    Methodological Naturalism versus The Naturalism Worldview.

    With regard to the scientific community there is a generally accepted approach to practicing science. In philosophical terms this approach is called “methodological naturalism”. This approach requires that we cannot evoke something unknown to explain evidence. Methodological naturalism is our best way of being sure of the things we can know, for instance by repeated observation we can be sure that birds come from eggs so we don’t need to evoke an unknown source to explain how birds are born. Thus a known plus a known equals a known.
    A problem occurs however, when we are faced with things we cannot know, for instance we cannot know how the first birds originated. It’s not that we are waiting to discover how they originated but rather, that the origin of birds is unknowable. We can use methodological naturalism to learn more about bird origins but we can’t use it to find out how the first birds originated. No method exists that can make the unknowable known. Thus a known plus an unknowable equals an unknowable.

    The “Naturalism Worldview” is an assumption that Nature and its laws are all that exist or; That anything outside of Nature is irrelevant.
    This worldview is quite similar to methodological naturalism in that it attempts to cancel out any unknowable sources as explanations for Existence. The problem is that we can’t know if naturalism is the true way to view reality, that naturalism is true is unknowable. The other problem is that the origin of Existence is also unknowable. An unknowable plus an unknowable equals an unknowable and therefore any decision about Existence and its origins is purely philosophical (mythological) and certainly not scientific.
    So while naturalism is a great position to adopt when dealing with the knowable it is clearly no more than a philosophical assumption when dealing with the unknowable.
    Those who have adopted naturalism as their worldview have adopted the foundation of their own mythology.
    Many believe that because methodological naturalism is the best way to do science, naturalism must therefore be the best way to view the world. Perhaps they think that they are being “scientific” by subscribing to naturalism; but as we have just seen, this is very far from the truth. It simply does not follow that the need for methodological naturalism in scientific practice means that naturalism is the true way to view reality. Naturalism may not be leading us toward the truth at all. For instance, if there are things outside of the natural material world, methodological naturalism provides no way of discovering them and the naturalism worldview presumes that they are not there at all.

  2. 2
    kairosfocus says:

    Myth: Kindly cf here on for a discussion of what is really going on behind the imposition of methodological naturalism on science, and here for a current discussion. Unfortunately, MN is in reality an ideological agenda that closes off science, not an epistemologically well warranted approach. That is why I have gone back to Newton above on the real valid form of the principle of uniformity and thinking based on regularities and causal patterns. KF

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