knows what follows from the accidents of the artificial body that is the commonwealth. Within natural philosophy, geometry, which lies at the base of the hierarchy in De corpore, takes as its object the accidents common to all bodies whereas physics takes as its object qualities, i.e., accidents of bodies as sensed by humans. This implies that the application of Hobbes’s generic method varies with object. As scholars have long realized, Hobbes’s actual procedure in physics differs from that of geometry and civil science since we are not privy to the underlying causes of the bodily qualities we sense.15 In physics one cannot define a quality by mentally constructing it, as one does with the generative definition of a square or when one imagines a commonwealth coming into being. Rather one must begin from observed effects, like the reddish hue of the setting sun or the passion of joy we feel when we watch it, and reason hypothetically to their possible causes. Since physics lies in the middle of the hierarchy of scientific knowledge providing the bridge between geometry and practical philosophy, if one assumes that unity means the sciences present a unified content, via an axiomatic-deductive method whereby all their conclusions trace back through a seamless chain of deduction to the same foundational definitions, then the divergent methodical procedure necessitated by the objects of physics appears to disrupt the unity of the whole.
In the face of these problems, one can 1) deny that Hobbes maintains a unity of theoretical and practical philosophy or 2) affirm a looser unity by denying that it is conditioned upon an axiomatic-deductive method. Advocates of 2) present evidence of Hobbes’s commitment to a non-deductivist unity. I draw on two recent views of this unity to propose a third. 2a) reads Hobbes’s sciences as unified not by a systematic content ultimately deduced from first principles, but by a common “demonstrative” method analogous to the geometrical method of construction.16 This strikes me as the correct strategy; however, though one finds procedures resembling constructions throughout Hobbes’s works, they cannot, as per his formal definitions constitute scientific demonstrations. Hence though they loosely connect practical philosophy with geometrical procedures, they cannot account for a moral science in Hobbes’s sense. 2a) also excludes physics from science. 2b) holds that Hobbes maintains the possibility of scientifically deducing a consistent body of theoretical and practical knowledge from first principles but includes alternative starting points and methods for non-philosophers to gain knowledge of practical philosophy.17 This too is promising, but to the extent that there is one method, it is an ideal that does no work. In practice, Hobbes proceeds as though physics and politics are independent domains with their own methods.
Despite these problems, 2) is better supported than 1). Hobbes’s view of scientific knowledge and generic definition of method point to one type of cognitive activity that constitutes scientific knowledge of all philosophical subjects. Regardless of whether one studies natural or artificial bodies, starts from cognitions of causes or effects, formal definitions or true cognitions attained by introspection, the process of methodical computation that charts the shortest route between causes and effects should be identical. This fits Hobbes’s aim of inaugurating a civil science to exorcise the Scholastic philosophy Empusa. Absent a unity of method for science, the boundaries between practical philosophy and religion will blur as non-scientific forms of cognition can then be invoked to confuse the rights and duties of subjects. Hobbes’s approach to identifying and removing the source of civil strife then falls apart. Hence overall 2) is the correct approach. I now draw on Hobbes’s context to propose a third variation, 2c).
Key is recognizing that Hobbes’s generic definition of method is just that. He next distinguishes method into what his contemporaries call universal method versus a method of proof for solving particular problems, known as particular method. Universal method was typically a preliminary hierarchical ordering of the concepts and definitions required for the discovery or teaching of knowledge of a subject, or both. It is distinct from method as a set of rules for scientific proofs, as found in Aristotle’s Posterior Analytics.18 Nonetheless, the two methods go hand in hand since universal method provides the systematic framework within which one generates different kinds of proofs by the particular method. This provides a third kind of unity for all scientific knowledge, rooted in method, with universal method providing a hierarchically ordered set of principles and definitions one requires as starting points for the deductive arguments one then makes in different domains to answer particular questions. Interpretation, 2c), allows for one computational activity that unifies all the sciences: namely, the rules of syllogistic reasoning for making valid propter quid demonstrations once one has the true principles, and applies the relevant definitions to the problem at hand. But to avoid willy-nilly attempts at deduction from any definitions, Hobbes’s method includes a preliminary methodical resolution of ideas and orderly composition into definitions, starting from the simplest concepts of geometry. This ensures unity at the level of first principles and the definitions one is permitted to take as starting points for scientific demonstrations at each level of inquiry. 2c) has been overlooked because just as Hobbes uses “demonstration” equivocally, he characterizes both activities as “computation” and labels methodical procedures that make up both the ordering computation and the syllogizing computation as analysis and synthesis.19 The two branches of method have thus been confused for one. I now disentangle them.
1.3 Analyses and Syntheses Reinterpreted in Context
The bifurcation of philosophical method into a universal ordering of subject matter and a particular method of demonstration was commonplace in the logic textbooks of Hobbes’s intellectual context (Hattab 2014). Hobbes makes a similar distinction: “Philosophers either seek scientific knowledge [Scientia] simpliciter or indefinitely, that is, having posed no certain question, they [seek to] scientifically know as much as they can …” (Hobbes 1999, 59; OL I.60) in which case they employ a method that is strictly resolutive and analytical to arrive at universal notions compoundable by synthesis into definitions; or they seek to scientifically know
the cause of some certain phenomena, or to at least discover something certain, such as whatever would be the cause of light, heat, heaviness, a proposed shape, and similar things; or in which subject a certain proposed accident would inhere, or for the purpose of a certain effect which is proposed to be generated from many accidents, which [ones] would conduce most powerfully towards it; or in which manner for the producing of a certain effect, the proposed particular causes ought to be conjoined. On account of this variety of things sought, sometimes the Analytic method, sometimes the Synthetic, and sometimes both is to be summoned.
(Hobbes 1999, 59; OL I.60–1)
Method aimed at unqualified knowledge uses resolution/analysis and composition/synthesis in the Scholastic sense to holistically know as much as possible about body. Here computation is conceptual ordering, which Scholastic contemporaries distinguish into “analysis” and “synthesis.” Hobbes next turns to the method for answering specific questions about the causes and inherence of particular accidents of body, which may be analytic, synthetic or both, depending on the inquiry. But here he uses the Scholastic terms pertaining to the ordering method for another set of operations, including syllogistic deductions. The second branch of his method gives Hobbes the flexibility to tailor the procedure for the shortest route between causes/explanations and effects/consequences to the context of inquiry. But Hobbes misleadingly uses “analysis” versus “synthesis” plus their derivatives to label procedures that take distinct forms in the particular method. I will thus refer to its operations as analysis2 and synthesis2.20
At root, analysis and synthesis, the basic operations of philosophical reckoning, are for Hobbes akin to mathematical subtraction and addition, respectively. Recall that he separates scientific knowledge from experience. Experience consists in sensing or remembering that there is something but cannot yield a causal explanation of it. Hobbes’s example is that I see something approaching me and as it gets closer my senses detect a certain shape and motion. All I know by experiential cognition is that this thing exists; I don’t know what it is and what its causes are. For that I require computation, which begins with something like subtraction, the mental operation of resolution
