Friday, 2 April 2021

A Concise Introduction to Logic, Patrick J. Hurley, Wadsworth, 2006, 9th ed,. 8.7, III, 14 p. 449

There are at most two scientists in the laboratory. At least two scientists in the laboratory are Russians.  No Russians are Chinese. Therefore, if Norene is a Chinese scientist, then she is not in the laboratory. (Sx: x is a scientist; Lx: x is in the laboratory; Rx: x is Russian; Cx: x is Chinese; n: Norene) / All accounting is shown below the proof due to blogger formatting constraints.

1.     (x)(y)(z)[(Sx • Lx • Sy • Ly • Sz • Lz) ⊃ (x = y v x = z v y = z)]

2.     (∃x)(∃y)(Sx • Lx • Rx • Sy • Ly • Ry • x ≠ y)

3.     (x)(Rx ⊃ ~ Cx)

∴ (Sn • Cn) ⊃ ~ Ln

4.     Sn • Cn

5.     Rn ⊃ ~ Cn

6.     Cn • Sn

7.     Cn

8.     ~ Rn

9.     (∃y)(Sm • Lm • Rm • Sy • Ly • Ry • m ≠ y)

10.  Sm • Lm • Rm • Sr • Lr • Rr • m ≠ r

11.  (y)(z)[(Sm • Lm • Sy • Ly • Sz • Lz) ⊃ (m = y v m = z v y = z)

12.  (z)[(Sm • Lm • Sr • Lr • Sz • Lz) ⊃ (m = r v m = z v r = z)

13.  (Sm • Lm • Sr • Lr • Sn • Ln) ⊃ (m = r v m = n v r = n)

14.  Rr ⊃ ~ Cr

15.  Rr • Sm • Lm • Rm • Sr • Lr • m ≠ r

16.  Rr

17.  ≠ n

18.  Rm ⊃ ~ Cm

19.  Rm • Sm • Lm • Sr • Lr • Rr • m ≠ r

20.  Rm

21.  ~ Cm

22.  ≠ n

23.  ≠ r • Sm • Lm • Rm • Sr • Lr • Rr 

24.  ≠ r

25.  ≠ r • m ≠ n • r ≠ n

26.  ~ (m = r v m = n v r = n)

27.  ~ (Sm • Lm • Sr • Lr • Sn • Ln)

28.  ~ (Sm • Lm • Sr • Lr • Sn) v ~ Ln

29.  Sm • Lm • Sr • Lr • Rm • Rr • m ≠ r

30.  Sm • Lm • Sr • Lr

31.  Sn

32.  Sm • Lm • Sr • Lr • Sn

33.  ~ Ln

34.   (Sn • Cn) ⊃ ~ Ln

4. ACP; 5. 3 UI; 6. 1 Com; 7. 6 Simp; 8. 5,7 MT; 9. 2 EI; 10. 9 EI; 11. 1 UI; 12. 11 UI; 13. 12 UI; 14. 3 UI; 15. 10 Com; 16. 15 Simp; 17. 8,16 Id; 18. 3 UI; 19. 10 Com; 20. 19 Simp; 21. 18,20 MP; 22. 7,21 Id; 23. 10 Com; 24. 23 Simp; 25. 17,22,24 Conj; 26. 25 DM; 27. 13,26 MT; 28. 27 DM; 29. 10 Com; 30. 29 Simp; 31. 4 Simp; 32. 30,31 Conj; 33. 28,32 DS; 34. 4-33 CP



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