Wegener's drift theory seemed more plausible than land bridges connecting all of the continents. But that in itself was not enough to support his idea. Another observation favoring continental drift was the presence of evidence for continental glaciation in the Pensylvanian period.
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Striae left by the scraping of glaciers over the land surface indicated that Africa and South America had been close together at the time of this ancient ice age. The same scraping patterns can be found along the coasts of South America and South Africa. Wegener's drift hypothesis also provided an alternate explanation for the formation of mountains orogenesis. The theory being discussed during his time was the "Contraction theory" which suggested that the planet was once a molten ball and in the process of cooling the surface cracked and folded up on itself.
The big problem with this idea was that all mountain ranges should be approximately the same age, and this was known not to be true. Wegener's explanation was that as the continents moved, the leading edge of the continent would encounter resistance and thus compress and fold upwards forming mountains near the leading edges of the drifting continents.
Wegener also suggested that India drifted northward into the asian continent thus forming the Himalayas. Wegener eventually proposed a mechanism for continental drift that focused on his assertion that the rotation of the earth created a centrifugal force towards the equator. View More by This Author. Description This is a science book. Theory of the Earth, Volume 2 of 4 James Hutton. Theory of the Earth, Volume 1 of 4 James Hutton. Hints towards the formation of a more comprehensive theory of life Samuel Taylor Coleridge.
Since nothing in the conception of a thing as moving or at rest, without regard to other things, could explain a change in its motion or rest, something outside that conception is required to do so. But it would be unsatisfying to take inertia as primitive—to say that bodies in fact do tend to persist in their states, though there is no reason to be discerned in their nature why they do so.
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To say this would be to take it that Spinoza accepted the Cartesian principle as Descartes understood it, while rejecting the grounds Descartes offered for it, and without providing any substitute for it. This is dissonant indeed with the general tenor of Spinoza's rationalism. This suggests that he had a different conception than did Descartes of both the nature and ground of that principle.
An intriguing shift in the language Spinoza uses in the PCP to articulate the Cartesian laws of motion is suggestive of how Spinozistic and Cartesian inertia may differ. This substitution arguably involves a shift in dynamical implication. PCP IIp17's invocation of conari , if we read it in this active sense, signals an ongoing effort, a continuous directedness, in this case, at homeostasis.
One must be quite circumspect in drawing inferences from this terminological shift on Spinoza's part. For one thing, the word for which conari is substituted, tendere , can have similar connotations itself, carrying the sense of a try or an attempt. Spinoza identifies this power as the essence of the individual IIIp7 , and further identifies its increase with the individual's increased power of action, as opposed to passion, that is, with an increase in power of self-determination as opposed to external determination IIIp And reading Spinozistic inertia this way, imputing to the body a continuous effort to move so as to maintain the state it would be in absent external determination, also suits it to ground the PLMM.
Given the symmetry of interaction, each of the bodies to an interaction, being externally determined to change by the other, will strive to resist change as far as it is able. Plausibly, then, the total change of state resulting from the resolution of the opposition of the interacting bodies will be the least total possible. This suggests, at least tentatively, that even in the PCP , Spinoza is at work attempting to shore up worries in the foundations of Cartesian physics that stem from the unduly passive Cartesian construal of the equation of body with extension.
Quite apart from the question whether Spinoza intended to impose this more active reading of inertial dynamics on Cartesian philosophy, either deliberately or unawares, he clearly made the striving conatus of individual modes an important centerpiece of the mature philosophy he presented in the Ethics. A main focus of this puzzlement is the extent to which IIIp6 represents a teleological element in Spinoza's natural philosophy.
It is certainly central to Spinoza's subsequent treatment of human psychology, according to which we strive to obtain those things that increase our power and to avoid those that diminish it. One ground for reading teleology out of the conatus principle and for regarding both teleology and that principle as fundamentally irrelevant to Spinoza's physical theory is that the latter's first explicit appearance in part III of the Ethics comes long after Spinoza presents his accounts of extended nature and the basic mechanics of modes thereof, indeed in a way that makes it very hard to see how any teleology could be involved at all.
Ip28 denies that any singular thing can be determined to exist or to produce an effect unless it has been so determined by a prior finite cause, ad infinitum. The use made of Ip28 in IIp9 suggests that Spinoza intends Ip28 to articulate not just a necessary condition on modal existence and determination, but the exclusive means by which finite modes are brought to existence and determined to have any particular effects.
This seems to allow no room for action of bodies in their own right, no residual space for any contribution to the motions of bodies of the active striving of the moving bodies themselves. In this light, the problem from the standpoint of the metaphysics of Extension — the basis of physical theory—is to explain why the specific configuration of a given existing mode makes any contribution at all to the determinations that result from the operation of external modal causes.
It would be rash to read Ip28 in such a way that the causal powers of a body owe everything to the contributions of extrinsic causes, and nothing to the intrinsic nature of the body itself. So the nature of an affected body makes a difference to the way it is affected extrinsically. This is not surprising. But then what explains why a body's nature makes a contribution to the way extrinsic influences determine it?
As we saw in the previous sections, some answer to this question is required to make sense of the PLMM, and hence of all of the collision laws. The notion, shared by the teleological reading of conatus and the active reading of Spinozistic inertia, that it is in the nature of bodies actively to strive of their own power, would seem to help.
But is it Spinozistic? We require a more probing examination into Spinoza's conception of the nature of individual bodies. As noted above, Spinoza accepts the basic Cartesian view that physical things are res extensa —extended things. However, whereas Descartes held that distinct bodies are distinct extended substances, Spinoza famously holds that there is but one substance—God or nature—and that distinct bodies are merely modes of this one substance, considered as extended.
Spinoza's substance monism is in part motivated by inadequacies in the Cartesian view. Descartes officially defines substance in terms of independence: But only God satisfies this definition, all other beings depending on God for their existence. So Descartes also allows for finite substances—minds and bodies—that are dependent only upon God.
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But it is only in an equivocal sense that both God and created, finite bodies and minds are substances. Spinoza will have none of this. For him, independence is the sine qua non of substance, and nothing that is not its own cause — nothing whose existence is not of its essence—is independent. Hence nothing finite and created is substantial. Further, since everything is either in itself or in another Ia1 , finite things like bodies are in substance, that is, they are in some way features of the one substance.
This denial of substantiality to bodies gives rise to an important interpretive issue. The traditional concept of a substance has at least two important strands. One is the idea we have already seen, of substance as independent. But another is the idea of a substance as an ultimate subject of predication, that is, as something of which properties or relations may be predicated, but which is itself never predicated of anything else.
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Does Spinoza mean to deny to bodies and other finite things this status as an ultimate subject as well? That is, is talk of bodies fundamentally to be construed for Spinoza as predicative or adjectival on substance? This matter is of the utmost importance for the understanding of Spinoza's physical theory, since deciding that Spinoza held bodies to be in fact ways substance is and adjectival on it, in accord with the former interpretation, requires that bodies as ordinarily conceived must be thought of as arising from and reducible to some more fundamental qualitative variation in spatiotemporal regions of extension.
This has the consequence, to some commentators salutary, of rendering Spinoza physical theory strongly prescient of contemporary physical views, in which ultimately physical nature is conceived as a field of gradient forces, bodies being not ultimate, but rather the consequences of particular local concentrations of certain classes of those forces, yielding certain characteristic effects in interactions, which effects we take as marking the presence of bodies.
Against the adjectival reading, and in favor of the view promoted by Curley that Spinozistic bodies and minds are ultimate subjects of predication, is Spinoza's persistent references to bodies as individuals and as things. The adjectival view of bodies, unlike the subjectival, must therefore face the difficult general question how individuals or things can be predicated of other individuals or things.
However, the question of how bodies are individuated—the principles according to which they are distinguished from one another and maintain identity through time and change—presents especially interesting and thorny difficulties for both the adjectival and subjectival views of bodies. While Descartes does claim at least most of the time that individual bodies are distinct substances, he does not invoke this claim in his official account of the individuation of bodies. The account he does offer is highly problematic.
Thus the distinction between bodies is constituted of distinctions in the motions of regions of extension. The circularity here is obvious, and crippling. Diversity and variety of bodies depends on motion, but motion depends upon a prior distinction between bodies. That Spinoza was aware of the problem Descartes' views had accounting for variety in extension is clear: But perhaps he did present all the elements of these matters, though in improper, hence inadequate, order.
But the PI seems to offer little help. Yet the text of the PI makes no appeal to the infinitude, eternality or expressive nature of extension or any other attribute. More importantly, at least on the face of it, the account of the individuation of bodies presented in the PI moves in much the same futile circle as that offered by Descartes.
That motion serves to individuate bodies is quite explicit in PIDL1: Spinoza, then, appears to accord with Descartes in taking bodies to be distinguished by their respective motion and rest. But motion and rest seem in the first instance to be determinations of bodies. So the motion of bodies seems to presuppose a prior ground of their individuation. Commentators have tried various strategies for finessing the apparent circularity in the PI's account of the diversity in matter. This reading arguably answers Spinoza's call to explain the variety in matter through an attribute that expresses eternal and infinite essence.
If God creates extended matter, and then, in a separate act, sets it in motion, the attribute of Extension would not suffice as an eternal expression of infinite essence, since it requires God's additional action in its expression of power. What then are they? Klever waxes vague and anachronistic here, straightaway seeking to validate his claim rhetorically by citing it as precedent of the view of contemporary physics: Hampshire contains similar remarks.
Jonathan Bennett's influential reading agrees that Spinoza's physical theory anticipates contemporary views. But rather than simply identifying motion and rest with energy or any other trope of contemporary physical theory, Bennett holds that the terms function as mere placeholders for some basic physical quality, unknown to Spinoza, but required to make sense of the appearance of bodies— ostensible things or subjects of predication — in the context of a metaphysics that holds that bodies, as modes rather than substances, are not things or subjects at all, but rather ways that the one substance is.
According to Bennett, Spinoza's Extension is, at the fundamental metaphysical level, a four dimensional field whose regions differ in the distribution and degree of this basic quality. Bodies are appearances, at one or more levels removed from this base, of the continuous path in this field constituted by relatively consistent local patterns of distribution of this quality. When the snow line recedes, there is no thing that changes its place; rather, there is a change in which regions of the landscape have the quality of being snow-covered, and that change describes a continuous path.
One might object to that this analogy is not clearly persuasive. Shifts of temperature lead to a thaw only because bodies—ice crystals and aggregates thereof—melt as temperature rises, and their boundaries recede along the backdrop of a very bodily landscape. Indeed, to thaw is just to pass from a solid to a liquid state, and solidity is a benchmark of the bodily.
If we excise these bodily aspects of the analogy, it is unclear how much of its explanatory force remains. But then it is unclear just how well qualitative variations of fields can explain the appearance of bodies. Perhaps if we knew more about this quality, the sense in which such continuous paths of patterns of it could appear as or constitute bodies would be clearer.
Furthermore, these quantities can be ascribed, he says, to the regions of extension themselves, rather than to bodies, thus overcoming the circularity problem we found in Descartes. But it is unclear that Spinoza's text can support this interpretation. In each mention, the force or resistance is attributed to a body. This strongly suggests that quantity of motion and rest, as force and resistance, are features of bodies.
Rather than showing how bodies could just be, or arise from, fields of such forces, the forces themselves seem to be characterized in ways that presuppose body; the circularity, then, remains. Individual bodies have an inherent stability, or robustness. They resist destructive incursion or change in their distinctive mode of endurance; they tend to persist in their configuration and motion in the face of opposition to this persistence.
If bodies either are, or are appearances of, persistent patterns of qualitative variation of extended regions, then it seems necessary, though hardly sufficient, that something about such patterns would have to account for this stability. But what might do so? One suggestion is that nothing accounts for this stability at all, and that the duration of a body is nothing more than the time through which a given complex ratio of motion and rest happens, de facto, to characterize regions of extension whose sum over time describes what can be construed as a continuous path.
There is nothing to prevent such spatiotemporally continuous patterns from occurring. But there is nothing in being a time slice of such a pattern that explains why the same pattern should also characterize any other spatiotemporal region continuous with it. There may, indeed must, be kinematic 'laws' describing how such patterns vary the scare quotes cause the counterfactual supporting status of such 'laws' would be secured only by Spinoza's necessitarianism , but nothing about any given time slice of such patterns accounts for the fact that they are subject to just those descriptive 'laws'.
Individual time-slices of such patterns would be wholly passive with respect to the persistence and trajectory of the pattern as a whole. A significant problem with this line [ 8 ] is that Spinoza uses manifestly active language to describe the doings of individuals.
And in IIIp6, on which the entire psychological theory of the second half of the Ethics depends, Spinoza claims that individual things strive to persevere in their being; his subsequent uses of the IIIp6 seem clearly to suggest that Spinoza intends this striving to be understood as an a active principle rather than a mere tendency. On the conception of individuals as ratios of motion and rest that simply happen to endure, none of this would make any sense at all. They cannot, for reasons already mentioned, be powers to move or to resist bodies. But to let the matter stand there would be simply to name the problem rather than to explain it.
But that is just to say that it manifests the powers it does because of the powers it has to do so — not very illuminating. Moreover, if a body's motion in a spatial field, including that of the simplest bodies, is just a change of location at which a given degree of power is instantiated, then there seems to be no means of explaining why a particular degree of power would necessarily change locations — move — continuously, as opposed to discontinuously.
But surely it is in the nature of bodies as explananda here that they are spatiotemporally continuous. But this would be consistent with the unlikely idea of discrete, discontinuous motion of a body, and indeed with the bi-location of bodies, that is, with the idea that a single body might be wholly present in each of multiple regions. But it is worth asking whether these doubts in fact rest on an inappropriate imaginative basis. It seems difficult imaginatively to represent variegated fields of energy, force, or any other quality in such a way as to make clear how bodies, with the persistent resistance and capacities for interaction we ordinarily represent them to have, could possible appear from or be constituted by them.
But this sort of failure of imaginative thinking cannot count against the acceptability of a theory from a proper Spinozistic perspective. On his view, our knowledge of body as an object of imagination is inherently inadequate. Our imaginative ideas of bodies in their corporeality are limited to the ideas of modifications of our own bodies. These in turn reflect only in a confused and partial way the natures of both the bodies with which we are affected and our own.
At no time is the full nature of any body reflected in any of the ideas we have through these affections, hence through anything we can imagine. Hence our imaginations cannot grasp the nature of body, and failure of the faculty of imagination to provide insight into the link between the fundamental basis for variety in matter and that variety itself is to be expected.
All of this is clear from IIp16— Any appearance of insight into the nature of body gleaned from the imagination is as likely to be illusion as illumination. But if we cannot come to an imaginative grasp of how bodies or their appearances might be constituted out of fields, then through what sort of intellectual act might we do so?
In the context of early modern philosophy of physical nature, and in particular the Cartesian philosophy in which Spinoza is steeped, the clarity and distinctness of mathematical ideas provides the contrast to the incompleteness and confusion of ideas of the imagination and sensation. And certainly the quantifiability of properly physical qualities, and consequently their comprehensibility within a closed system of mathematical laws, is of the utmost importance to the credentials of the fundamental notions of the contemporary physical theory Spinoza is alleged to have anticipated.
The scientific success of classical mechanics, relativity theory, and, especially, quantum mechanics owes much more to the predictive and formal success of these theories than it does to our abilities to represent phenomena in the imagination that answer to the basic physical elements they countenance.
Point masses, gravitational forces operating at a distance, curvatures of space time, finite but unsurpassable velocities, and wave-packets all seem to surpass our powers of imaginative representation. We have no real capacity to imagine how the solid table on which my computer rests can be identical to both a swirling cloud of particles and a warp in the very fabric of space.
On the other hand, these fundamental scientific notions can be rendered mathematically, placed within a system of laws, and employed to great effect in predicting and manipulating, hence effectively representing, the same nature we represent imaginatively. Thus perhaps the proper criterion, or at any event a proper criterion, for the success of an Spinozistic account of variety in matter and its individuation into bodies is the quantifiability of the basic properties in which it proceeds. Gabbey stresses this line with admirable clarity.
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That Spinoza did not himself provide the mathematicization of his notion of motion-and-rest that would render his theory of body non-circular and sufficiently clear to be understood or imagined does not entail that this cannot be done. Garrett, whose account we have already examined, nods his head in this direction. Matson also places weight on the possible quantifiability of motion and rest as a means of in rendering it a clear and distinct, non-imaginary basis for our understanding of the individuation of bodies, taking the idea of an atomic number as his model:.
Matson piggybacks on to this analogy the formula for the identity of any living thing supposedly found in its genetic code. Treating such structures as representable by formulae enhances the impression that they are expressible in numerically quantifiable terms. Such attempts to interpret motion and rest as numerically expressible quantities constitute efforts to make Spinoza's physical theory relevant to contemporary science, by displaying how it can conform to, and even constitute a blueprint for, its mathematical structure.
They stand, then, as responses both to Gabbey's implication that because Spinoza does not say how his notion of motion and rest can be expressed mathematically, his views are too vague and sterile to be of such contemporary relevance, and to the difficulties we have seen, in conceiving how motion and rest, as we conceive them imaginatively, could possibly serve to individuate bodies. But at the end of the final section of this article, we will see that, quite apart from the vagueness, anachronism Spinoza anticipating not just Mendeleyev, but also Watson and Crick?
In the previous sub-section, we saw reasons for doubting the adequacy of readings that treat the PI's talk of motion and rest as constituting his entire account of individuation. This section considers an alternative interpretation of Spinoza's approach to individuation. This account appeals to the notion of individuating essences. This suggests that the essence of an individual is particular to that individual, since otherwise, what belongs to it could be given without that individual being posited, so long as some other individual with that essence were posited.
But how are we to conceive essences, and how can they help solve the problems we have encountered with claiming the PI, with its talk of motion and rest, provides Spinoza's full account of individuation? Here Spinoza writes as if a body's essence and its form are one and the same. In each of PIl4, 5 and 6, Spinoza speaks of bodily persistence in terms of its parts keeping the same ratio of motion and rest. These are plainly meant to state conditions on individual persistence.
These lemmas seem to equate nature and form. Moreover, Spinoza implies that so long as this form or essence is retained, a thing is not destroyed. IIIp4 is worthy of particular attention here. This includes both the thing's essence and those properties following from it. Such properties, in the thing in one sense but external to it in another, may be destructive of the thing.