TIP of the day (logic): Science, religion and logic

MJ. Smith

Many of the arguments between science and religion are based on a misunderstanding of the various types of logic and the knowledge that we gain through them.

The basic types of logic with very simplified definitions are:

• Deductive logic - here if the premises are true the conclusion must be true
• Inductive logic - from observing a number of particular instances we come to a general conclusion which is provisionally accepted as true until instances to the contrary are observed.
• Abductive logic - from incomplete information abductive logic reasons to the best explanation.
• Defeasible reasoning - forms of reasoning that produces a contingent statement
• Probabilistic reasoning
• Statistical reasoning

Formally these may be defined as:

• Deductive (from meaning postulate, axiom, or contingent assertion): if p then q (i.e., q or not-p)
• Defeasible (from authority): if p then (defeasibly) q
• Probabilistic (from combinatorics and indifference): if p then (probably) q
• Statistical (from data and presumption): the frequency of qs among ps is high (or inference from a model fit to data); hence, (in the right context) if p then (probably) q
• Inductive (theory formation; from data, coherence, simplicity, and confirmation): (inducibly) "if p then q"; hence, if p then (deducibly-but-revisably) q
• Abductive (from data and theory): p and q are correlated, and q is sufficient for p; hence, if p then (abducibly) q as cause

Science is based on inductive and abductive logic. Scientific truths are always a revisable, best explanation truths. Computer medical diagnosis programs are an example of abductive logic in action.

Legal reasoning is based primarily on defeasible reasoning.

Theology in religions based on revelation are primarily deductive reasoning. Mathematics is also built on deductive reasoning.

Science and religion often clash unnecessarily. Religion can say "God created the universe" but that statement doesn't allow us to make predictions on which we can act. Science can build a theory that we can use to make predictions/building explanations but it is only the best model we have at this time. And sometimes we know that the best model we have for making predictions/building explanations is not the best model we have ... it is simply good enough for our purposes e.g. the continued use and teaching of Newtonian physics.

When dealing with a person who believes that science is the only source of knowledge and that we have pretty much explored the entire universe two primary points need to be made:

• the provisional nature of scientific knowledge
• the limited current domain of science compared to the domain of experience - we don't know where what we currently don't know will take us