The Structure of Physics VIII.5

The structure of Physics VIII.5

Chapter 5 picks up immediately on the preceding passage of Chapter 4 (255b31-256a3).

What is taken to be the start of Ch. 5(Τοῦτο δὲ διχῶς κτλ.) does not look like a fresh start, or even as a break in Aristotle’s thought.It is encouraging that Ch. 5 ends at a natural place, at line 258b9, but one wonders whether the text should be partitioned differently, namely such that Ch. 5 goes from 255b31 (now in Ch. 4) to 257a33, and then the rest of Ch. 5, from 257a33 to 258b9, should form Chapter 6, and what is now Chapter 6 should become Chapter 7 etc. Thus we would have two chapters, each corresponding to one well rounded part of the text.

Chapter 5 has two parts:

Part 1: from 256a4 (continuing without interruption from Ch. 4, 255b31) to 257a31,

inwhich Aristotle argues that the first mover in a series of moved things must be a self-mover.

Part 2: from 257a31to 258b9, in which Aristotle argues that the part of a self-

mover that causes motion is unmoved.

Part 1 is itself divided in two sections:

Section1: from 256a4 (continuing without interruption from Ch. 4, 255b31) to 256b3, in which Aristotle supplies two arguments for the view that the first mover in a series of moved things must be a self-mover.

Argument 1 (from the moved thing, 256a3-21)

Argument 2 (from the mover, 256a21-b3)

Section 1 willbe presented by FilipGrgic

Section2: from 256b3-257a33, in which Aristotle supplies a further, dilemmatic reductioargument for the view that the first mover in a series of moved things must be a self-mover. The third argument proceeds in two main steps, with one intermediate step between them.

Section 2can itself be divided into three chunks:

Chunk 1 (256b3-13): Introduction of Argument 3 and refutation of the

first horn of the dilemma (“the moved mover moves per accidens”)

Chunk 2 (256b14-27): The intermediate step: there are three aspects in

every instance of motion.

Chunks 1 and 2 will be presented by PavelGregoric

Chunk 3 (256b27-257a31): Refutation of the second horn of the

dilemma (“the moved mover moves per se”) and the conclusion of Argument 3.

Chunk 3 will be presented by Peter Lautner

Part 2 is divided into five sections:

Section 1: Elimination of three models of a self-mover (257a33-257b35).

(i) Model 1: A self-mover moves itself as a whole (257a33-b13).

(ii) Model 2: A self-mover moves itself because its parts move each other (257b13-26).

(iii) Model 3: A self-mover moves itself because its parts – one or more – are

self-movers (257b26-35).

Section 2: The conclusion — one part of the self-mover is an unmoved mover and another is

moved (258a1-5)

Section 3: A demonstration of the minimal structure of a self-mover (258a5-27)

Section 4: A puzzle about the divisibility of the minimal self-mover (257b27-258b4)

Section 5: Restatement of the conclusion: The primary mover is unmoved (258b4-9)

Part 2 will be presented by NadavRatzabi