Combining Texts

All the ideas for 'What is Logic?st1=Ian Hacking', 'III.12 On physiognomy' and 'Human Nature'

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18 ideas

1. Philosophy / D. Nature of Philosophy / 8. Humour
Laughter is a sudden glory in realising the infirmity of others, or our own formerly [Hobbes]
2. Reason / D. Definition / 3. Types of Definition
A decent modern definition should always imply a semantics [Hacking]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL
Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C' [Hacking]
Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with [Hacking]
'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking]
5. Theory of Logic / A. Overview of Logic / 4. Pure Logic
The various logics are abstractions made from terms like 'if...then' in English [Hacking]
5. Theory of Logic / A. Overview of Logic / 5. First-Order Logic
First-order logic is the strongest complete compact theory with Löwenheim-Skolem [Hacking]
A limitation of first-order logic is that it cannot handle branching quantifiers [Hacking]
5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
Second-order completeness seems to need intensional entities and possible worlds [Hacking]
5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / a. Logical connectives
With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically [Hacking]
5. Theory of Logic / E. Structures of Logic / 4. Variables in Logic
Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking]
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking]
16. Persons / F. Free Will / 5. Against Free Will
A man cannot will to will, or will to will to will, so the idea of a voluntary will is absurd [Hobbes]
17. Mind and Body / E. Mind as Physical / 1. Physical Mind
Conceptions and apparitions are just motion in some internal substance of the head [Hobbes]
22. Metaethics / B. Value / 1. Nature of Value / f. Ultimate value
There is no absolute good, for even the goodness of God is goodness to us [Hobbes]
22. Metaethics / B. Value / 2. Values / e. Death
Apart from the fear, dying is an easy duty [Montaigne]
22. Metaethics / C. The Good / 2. Happiness / c. Value of happiness
Life has no end (not even happiness), because we have desires, which presuppose a further end [Hobbes]
25. Social Practice / F. Life Issues / 5. Sexual Morality
Lust involves pleasure, and also the sense of power in pleasing others [Hobbes]