One thing Empiricism (E) got right is that there are no foundational assumptions of general scientific utility that are empirically inviolable. Rationalists (R) once thought otherwise, thinking that the basics of the mechanical philosophy (matter is geometrical and all forces are contact forces) as well as an innate appreciation of some of God’s central features could undergird permanent foundations for investigation of the physical world. One of Newton’s big debates with the Cartesians revolved around this point and he argued (as convincingly examined hereby Andrew Janiak) that we have no privileged access to such theoretical starting points. Rather, even our most basic assumptions are subject to empiricalevaluation and can be overturned.
This is now the common view. The Rs were wrong, the Es right. Or at least someof them were. Descartes and his crew were metaphysical foundationalists in that they took the contours of reality to be delivered via clear and distinct innateideas. As these ideas reflected what had to be the casethey served to found physical inquiry in a mechanical view of the world. So for Rs innate ideas were critical in the sciences in that they were metaphysically foundational. Newton denied this. More exactly, he denied that there were empirically unassailable foundations for natural philosophy. And he did this by arguing that even foundational assumptions (e.g. the mechanical philosophy) were subject to experimental evaluation. This he proceeded to do in the Principia Andrew Janiakwhere he argued that the mechanical philosophers had it all wrong, and that mass and gravity were inconsistent with mechanism and so false. Great argument.
As Janiak tells the story, three features of Newton’s story really made his conclusions convincing. First, he provided a mathematical formulation of the force laws and the law and gravitation. Second, he showed how these unify terrestrial and celestial mechanics. That they wereunified was a staple of Cartesian mechanical thinking. However, they could not show that this conviction was scientifically justifiable. Newton unified the two domains via gravity (plus he threw in the tides as a bonus) thus achieving what the mechanical philosophers wanted by using a force they despised. Third, Newton provided a principled account for Galileo’s observation that acceleration was independent of the shape/size/density of the accelerating objects. Why this should be so was a real puzzle, and an acknowledged one. The link between gravitation and mass that Newton forged had this independence fall out as a trivial consequence. The second and third achievements were substantive within the framework of Cartesian physics (they solved problems that Cartesians recognized as worthy of explanation) but they were inconsistent with Cartesian mechanical philosophy (because they were based on Newton’s conceptions of mass and gravity), as was widely understood. This is why Newton’s physical interpretation of his formal work was resisted, though everyone agreed that the math was wondrous. The problem was not the math, but what Newton took the math to mean.
The Janiak book goes into lots of detail regarding Newton’s argumentative approach to arguing against Cartesian orthodoxy. It is a really great read. The principle form of the argument goes as follows: it is possible to know thatsomething is true without knowing exactly howit can be.This involved unpacking Newton’s famous dictum that the does not feign hypotheses. This Janiak notes does not mean that Newton did not advance theories. Clearly he did. Rather Newton meant that he believed that he could both say that he knew something to be the case and that he did not know exactly how what he knew to the case could be the case. Sound familiar? This is a critical distinction and Newton’s point is that unless one carefully distinguishes the questions one is asking it is very hard to evaluate the quality of the answers. Some data for some questions can be completely compelling. The same data for other questions hardly begin to scratch the surface.
Newton showed that it is both possible to know thatGravity is real and not know exactly whyit has the properties we know it to have or even to exactly know whatit is (a relation or a quality). What Newton did know was that one could believe thatgravity was real without thinking that it was an inherent property of bodies that acted at a distance. He insisted that local action was consistent with gravity (there was no contradiction between the two) even though he did not know how it could be (he had no constructive theory of local action that included gravity).
I would have put things somewhat differently: Newton knew that gravity existed and what its signature features were and some central cases of its operations. He had an effective theory. But he did not believe that he had a fundamental account of gravity, though he knew that there could not be a mechanical explanation of these gravitational effects. Moreover, he knew that nothing known at the time implied that it was inconsistent with local action of some other yet to be determinedkind. So, he knew a lot but not everything, and that was good enough for him.
Note what convinced contemporaries: unification, and explanation of outstanding generalizations. So too today: we want to unify distinctive domains in syntax (MP requires this) and want to explain why the generalizations we appear to have discovered hold. This is the key to moving forward, and imitating Newton is not the worst path forward.
So, Eism did come out right on this point, but most Es did not. Newton was somewhat of an outlier on these foundational matters. He rightly understood that Cartesian metaphysics and its innate ideas window into reality would not wash. But he did not appear to embrace an Eist epistemology (or at least theory of mind). Unlike many, he did not endorse the view that there are no ideas in the intellect that are not first in the senses. Thus, his beef with Rists was not their nativism but their supposition that being innate conferred some kind of privileged metaphysical status. The way Newton short circuited the metaphysical conclusions was by showing that they did not hold up to experimental and theoretical scrutiny. He did not argue that the ideas could not be useful because they could not exist (i.e. there are no innate ideas) or that the only decent ideas were those based in perception. This was fortunate for curiously the Eists did not really grasp N’s basic take home message: ideaswherever they come fromrequire scientific validation through experiment and theory. And every part of every theory is in principle up for grabs, whatever its psychological source. Eists have tended not to understand that this was Newton’s message and have concluded that because Newton showed that Rist foundationalism failed that it failed because it countenanced innate ideas.
But this was not the problem. The problem came with the added assumption that innate ideas in virtue of being innate are empirically unassailable. Curiously, Eists came up with their own form of foundationalism based on their view that the only good idea are the ones based in the senses. This idea didn’t turn out very well either and gave rise to its own forms of foundationalism, also false by Newton’s standards.
So, Rs were wrong about the relation of ideas to truth even though they were largely right about the psychology. Newton was right that there are no useful a priori foundations for the sciences (i.e. foundations that are not ultimately empirically justified). Es were right in that they believed that Newton did show that Rism was wrong to the degree that it was foundationalist. Where Es got lost is in rejecting the Rish psychology becauseit failed to provide metaphysical foundations. Eism ended up looking for epistemological foundations that would demarcate legit (i.e. scientific thinking) from non legit thinking (everything else). Eists pursued the idea that if one grounded ones ideas in the senses will guarantee good foundations. Newton would not have approved. The right conclusion is that that there are no epistemological shortcuts to good science.
These are two questions that, though related, should not be confused. I have argued that they often have been within linguistics too. Thathumans have an FL that undleries their unique capacity to acquire language is almost a tautology, IMO. How FL allows humans to do this is a substantive problem that we have just started to crack.