11 ideas
| 3338 | Numbers have been defined in terms of 'successors' to the concept of 'zero' [Peano, by Blackburn] |
| Full Idea: Dedekind and Peano define the number series as the series of successors to the number zero, according to five postulates. | |
| From: report of Giuseppe Peano (works [1890]) by Simon Blackburn - Oxford Dictionary of Philosophy p.279 |
| 13949 | All models of Peano axioms are isomorphic, so the models all seem equally good for natural numbers [Cartwright,R on Peano] |
| Full Idea: Peano's axioms are categorical (any two models are isomorphic). Some conclude that the concept of natural number is adequately represented by them, but we cannot identify natural numbers with one rather than another of the isomorphic models. | |
| From: comment on Giuseppe Peano (Principles of Arithmetic, by a new method [1889], 11) by Richard Cartwright - Propositions 11 | |
| A reaction: This is a striking anticipation of Benacerraf's famous point about different set theory accounts of numbers, where all models seem to work equally well. Cartwright is saying that others have pointed this out. |
| 18113 | PA concerns any entities which satisfy the axioms [Peano, by Bostock] |
| Full Idea: Peano Arithmetic is about any system of entities that satisfies the Peano axioms. | |
| From: report of Giuseppe Peano (Principles of Arithmetic, by a new method [1889], 6.3) by David Bostock - Philosophy of Mathematics 6.3 | |
| A reaction: This doesn't sound like numbers in the fullest sense, since those should facilitate counting objects. '3' should mean that number of rose petals, and not just a position in a well-ordered series. |
| 17634 | Peano axioms not only support arithmetic, but are also fairly obvious [Peano, by Russell] |
| Full Idea: Peano's premises are recommended not only by the fact that arithmetic follows from them, but also by their inherent obviousness. | |
| From: report of Giuseppe Peano (Principles of Arithmetic, by a new method [1889], p.276) by Bertrand Russell - Regressive Method for Premises in Mathematics p.276 |
| 5897 | 0 is a non-successor number, all successors are numbers, successors can't duplicate, if P(n) and P(n+1) then P(all-n) [Peano, by Flew] |
| Full Idea: 1) 0 is a number; 2) The successor of any number is a number; 3) No two numbers have the same successor; 4) 0 is not the successor of any number; 5) If P is true of 0, and if P is true of any number n and of its successor, P is true of every number. | |
| From: report of Giuseppe Peano (works [1890]) by Antony Flew - Pan Dictionary of Philosophy 'Peano' | |
| A reaction: Devised by Dedekind and proposed by Peano, these postulates were intended to avoid references to intuition in specifying the natural numbers. I wonder if they could define 'successor' without reference to 'number'. |
| 15653 | We can add Reflexion Principles to Peano Arithmetic, which assert its consistency or soundness [Halbach on Peano] |
| Full Idea: Peano Arithmetic cannot derive its own consistency from within itself. But it can be strengthened by adding this consistency statement or by stronger axioms (particularly ones partially expressing soundness). These are known as Reflexion Principles. | |
| From: comment on Giuseppe Peano (Principles of Arithmetic, by a new method [1889], 1.2) by Volker Halbach - Axiomatic Theories of Truth (2005 ver) 1.2 |
| 17635 | Arithmetic can have even simpler logical premises than the Peano Axioms [Russell on Peano] |
| Full Idea: Peano's premises are not the ultimate logical premises of arithmetic. Simpler premises and simpler primitive ideas are to be had by carrying our analysis on into symbolic logic. | |
| From: comment on Giuseppe Peano (Principles of Arithmetic, by a new method [1889], p.276) by Bertrand Russell - Regressive Method for Premises in Mathematics p.276 |
| 604 | Knowledge is mind and knowing 'cohabiting' [Lycophron, by Aristotle] |
| Full Idea: Lycophron has it that knowledge is the 'cohabitation' (rather than participation or synthesis) of knowing and the soul. | |
| From: report of Lycophron (fragments/reports [c.375 BCE]) by Aristotle - Metaphysics 1045b | |
| A reaction: This sounds like a rather passive and inert relationship. Presumably knowing something implies the possibility of acting on it. |
| 14586 | Physical causation consists in transference of conserved quantities [Dowe, by Mumford/Anjum] |
| Full Idea: For Dowe physical causation consists in transference of conserved quantities. | |
| From: report of Phil Dowe (Physical Causation [2000]) by S.Mumford/R.Lill Anjum - Getting Causes from Powers 10.2 | |
| A reaction: [see Psillos 2002 on this] This is evidently a modification of the idea of physical causation as energy-transfer, but narrowing it down to exclude trivial cases. I guess. Need better physics. |
| 4787 | Causation interaction is an exchange of conserved quantities, such as mass, energy or charge [Dowe, by Psillos] |
| Full Idea: Dowe argues that a 'causal process' is a world line of an object with a conserved quantity (such as mass, energy, momentum, charge), and a 'causal interaction' is an exchange between two such objects. | |
| From: report of Phil Dowe (Physical Causation [2000]) by Stathis Psillos - Causation and Explanation §4.4 | |
| A reaction: This looks very promising. Nice distinction between causal process and causal interaction. 'Conserved quantities' is better physics than just 'energy'. We can hand causation over to the scientist? |
| 4788 | Dowe commends the Conserved Quantity theory as it avoids mention of counterfactuals [Dowe, by Psillos] |
| Full Idea: Dowe commends the Conserved Quantity theory because it avoids any mention of counterfactuals. | |
| From: report of Phil Dowe (Physical Causation [2000]) by Stathis Psillos - Causation and Explanation §4.4 | |
| A reaction: Clearly the truth of a counterfactual is quite a problem for an empiricist/scientist, but one needs to distinguish between reality and our grasp of it. We commit ourselves to counterfactuals, even if causation is transfer of conserved quantities. |