The dispute between Clarke and Leibniz mentioned above indicates that Newton’s
views did not meet with universal acceptance. Leibniz was the main opponent of Newton’s
banishment of active power from the material world, and the source of an alternative line of thought on the nature of physical things. Educated at first in the Aristotelian school,
Leibniz embraced the mechanical philosophy in his youth.13 He abandoned his adherence
to it, however, upon concluding that it was unable to give an account of the observed
properties of matter, and explicitly set out to defend and incorporate certain Aristotelian
notions in his metaphysics.
Accepting the point that matter conceived of as characterised solely by shape and
motion was necessarily passive, he rejected Newton’s view that its activity resulted from
divine intervention. Instead, he argued that the mechanical philosophy’s view of matter
was false, that physics required the postulation of active forces that belonged to the nature
of physical things, and that the Aristotelian notion of substantial form should be revived to
give an account of these forces. Indeed, he went further, and argued that all there is to the
nature of physical things are their powers to act and to be acted upon. (This talk of active
forces in things gets reinterpreted in his peculiar metaphysics as talk of the harmonised
changes within isolated monads, but when Leibniz is actually doing physics, he uses the
concept of active force as an explanatory principle.) His views on the active nature of
matter were accepted and used by Joseph Priestley and Roger Boscovich, who defined
atoms in Leibnizian fashion as centres of fields of force. Boscovich in turn exerted an
important influence on Michael Faraday and his development of field theory.14 Faraday
asserted a Leibnizian view of matter, saying of it that ‘the substance consists in the
powers’. (Harman 1982, p. 77.) Boscovich’s influence continued in James Clerk Maxwell15
and Lord Kelvin, who remarked that ‘My present assumption is Boscovichianism pure and
simple’. (Whyte 1961, p. 191.) Thus, as the neo-Aristotelian Brian Ellis remarks,16 there is
an important tradition stemming from Leibniz that endorses the Aristotelian notion of
active powers in things, and that gave rise to significant scientific achievement.
It is instructive to consider Leibniz’s disagreements with Aristotelian views as well as
his agreements, since they exemplify the main objections raised to Aristotelianism. He
complains that the scholastics thought they could ‘explain the properties of bodies by
mentioning forms and qualities, without going to the trouble of examining their method of
operation: as if someone thought it sufficient to say that a clock has a time-indicative
quality which comes from its form, without considering what all that consists in.’ (Leibniz
1973, p. 20.) He also criticises scholasticism for holding what he calls the ‘physical influx’
view of causation; ‘the way of influence is that of ordinary philosophy [viz. scholasticism];
but as it is impossible to conceive of either material particles, or immaterial species or
qualities as capable of passing from one of these substances to the other, we are obliged to
abandon this view’. (Leibniz 1973, p. 131.) This conceives of the Aristotelian understanding
of causation as involving the literal passing of some entity from the thing that is a
cause to the thing that is being causally affected, with the entities being either material
particles, or actual qualities of things––as if, when a seal is pressed on wax, the actual
shape of the seal, the particular configuration that belongs to that particular seal, is
somehow taken from the seal and passed on to the wax. There are in fact contemporary
advocates of theories of causality that have some resemblance to ‘physical influx’ ones,