Portal:Scientific method/Did you know
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... that John Stuart Mill's canons form a systematic heuristic for debugging a problem?
- Method of agreement: If a single common factor exists in all cases where a phenomenon occurs, then we can attribute the phenomenon to that factor.
- Method of difference: If one set of circumstances leads to a given phenomenon, and another set of circumstances does not, and the sets differ only in a single factor that is present in the first set but not in the second, then the phenomenon can be attributed to that factor.
- Method of agreement and difference: Also called simply the "joint method of agreement and difference", this principle simply represents the application of the methods of agreement and difference.
- Method of residues: If a range of factors are believed to cause a range of phenomena, and we have matched all the factors, except one, with all the phenomena, except one, then the remaining phenomenon can be attributed to the remaining factor: "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." — Sherlock Holmes in "A Scandal in Bohemia" by Sir Arthur Conan Doyle.
- Method of concomitant variations: If across a range of circumstances leading to a phenomenon, some property of the phenomenon varies in tandem with some factor existing in the circumstances, then the phenomenon can be attributed to that factor. For instance, suppose that various samples of water, each containing both salt and lead, were found to be toxic. If the level of toxicity varied in tandem with the level of lead, one could attribute the toxicity to the presence of lead.
