Hazards of propositional logic
Hazards of propositional logic
Scientists use propositional logic sparingly because it's extremely sensitive to misleading premises.

Classic example of propositional logic:
"Horses have an even number of legs. In the back they have two legs, and in front they have fore-legs. This makes six legs, which is an odd number of legs for a horse to have. But the only number that is both even and odd is infinity. Therefore, each horse has an infinite number of legs."
Critics of evolution often employ propositional logic. For example:
"Evolution is false because intermediate fossils are missing."
This is a conjunction of three propositions:

1- Evolution requires intermediates
2- There should be fossils of these intermediates
3- These fossils should have been found
Proposition 1 is generally true. Proposition 2 is not always true. Proposition 3 is not always true.

Another example:
"Life is too complicated to have evolved"
This involves two propositions:
1- Life is complicated
2- Complicated things can't arise by evolution
In this case proposition 1 is true. Proposition 2 is consistent with everyday experience, but not universally true.

Another example:
"Radioactive dating is unreliable"
This is a conjunction of:
1- Objects can be dated by radioactive methods
2- Some radioactive dates are preposterous
Proposition 1 is true. Proposition 2 assumes that the radioactive measurements satisfy the conditions necessary for accurate dating. Where measurements are preposterous they in fact don't satisfy the conditions for reasons that are usually obvious.

One more example:
"Alternatives to evolution should be discussed in science class"
This statement includes propositions:
1- There are alternatives to evolution
2- These alternatives are scientific
Here proposition 1 is true and proposition 2 is false

Dubious premises make propositional logic a minefield. Scientists employ it cautiously. Abusing propositional logic is a standard rhetorical "trick". Uncritical use of propositional logic degrades critical thinking skills.

The Discovery Institute is notorious for employing false premises.