JMagasin Bioethics Discussion Section 8

Happy Thanksgiving!

Deductive arguments review

See Weston (ch. VI) for more info and for some extended arguments broken down into the basic forms below.

modus ponens

  If 'p' then 'q.'              If something is made of gold, then it's a time machine.
  'p.'                          The ring is gold.
  Therefore, 'q.'               Therefore the ring is a time machine.
Is the example valid (structurally correct)? Sound (true in this world)?

modus tollens

  If 'p' then 'q.'              If it rained, then the grass is wet.
  Not 'q.'                      The grass is not wet.
  Therefore, not 'p.'           Therefore, it did not rain.
Note that 'not p' does not imply 'not q.' I.e. the "converse" need not hold since other things may cause 'q.'

hypothetical syllogism

  If 'p' then 'q.'              If it rained, then the grass is wet.
  If 'q' then 'r.'              If the grass is wet, then we should not
                                  turn on the sprinklers.
  Therefore, if 'p' then 'r.'   If it rained, then we should not turn
                                  on the sprinklers.

disjunctive syllogism

  Either 'p' or 'q.'            Either we'll have chicken or turkey.
  Not 'p.'                      We can't have chicken on Thanksgiving.
  Therefore, 'q.'               Therefore, we'll have turkey.
Does it matter if or means 'p or q but not both?' (No.)


  Either 'p' or 'q.'             Either the iocaine powder is in my goblet or yours.
  If 'p' then 'r.'               If mine, then I cannot drink the wine in front of me.
  If 'q' then 's.'               If yours, then I cannot drink the wine in front of you.
  Therefore, either 'r' or 's.'  Therefore, either I cannot drink the wine in front of
                                   me or I cannot drink the wine in front of you.
Is this argument valid? Is this argument sound? :)


The following statements sound somewhat reasonable. However, to really understand them and to check for assumptions (unstated premises), it is insightful to give them a more formal structure using the deductive forms above.

Your task: For the statements below, flesh out the argument to make it valid. Figure out what premises are missing, and turn the statement into a formal argument using the deductive forms above. Sub-arguments are fine, and you may want to use several of the above forms.

  1. Golden Rice has elevated vitamin A levels. Since vitamin A deficiency leads to terrible health issues such as blindness, we ought to help developing countries combat vitamin A deficiency with Golden Rice.
  2. Proper informed consent for advanced cancer patients considering participation in a clinical trial should require guidance from an attorney not related to the patient-subject.
  3. Animal caretakers should be integrated into research labs because they are obligated to protect animals because of their expertise.
  4. Forced inoculations of military personnel against biological agents (e.g., anthrax) is ethical because, unlike civilians, they don't have a choice.

More practice, and for discussion

The following excerpts are from from the Lawrence J. Nelson required reading. Try to lay out the formal structure as above.

  1. Embryos are morally considerable in part "because they are valued ... by sincere moral agents whose attributions of moral status must be given serious consideration as well as some deference and weight."
    Nelson's "principle of evaluative respect and accomodation."
    1. "Embryos are in a morally unique relationship with the persons who deliberately used their gametes to bring them into existence. For those persons and only those persons, embryos are genetically a literal part of them and have the potential to become their children. Consequently, these embryos have some moral status due to their unique relationship with the gamete sources."
    2. "But this potential has moral significance only if the woman who provided the egg, or some other woman, voluntarily chooses to gestate the embryo with the consent of both gamete sources. Embryos do not have moral status simply because they have theoretical potential to develop into born persons. Embryos have true potential only if they are in the process of being gestated by some particular woman."
  2. "...there are sufficient scientific reasons to believe that research with stem cells could someday result in significant benefits for suffering and injured persons. This is a great moral good; it is not mere caprice or frivolity that underlies the promise of stem cell research. Therefore, it is ethically permissible for embryos, which have a modest moral status but not the status of persons, to be destroyed in the course of responsible stem cell research -- provided they are destroyed with a sincere attitude of respect, for there is a moral loss here -- something morally valuable is being destroyed, and provided they are used only with the voluntary, informed consent of both gamete sources."