Nature is complex and complicated. To discover the cause of a phenomenon is not that easy a matter. It requires at times great acumen and effort to find out the cause of an event. But the question is-what method should be adopted to find out the cause of an event! Different methods have been suggested which are used in the process of scientific explanation to discover the cause of a phenomenon. Such methods are called the experimental methods.
But before the real cause of an event is known the irrelevant factors need to be eliminated. The non-essential antecedents should be rejected so that it would pave the way to discover the real cause of a phenomenon.
Francis Bacon has suggested some methods that can enable to reject the unnecessary antecedents from the fold of the supposed cause. They are:
1. An absent circumstance cannot be the cause.
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2. A circumstance in whose presence the phenomenon (effect) does not occur cannot be the cause.
3. The cause and the effect vary together and the variations are proportional.
J. S. Mill later on made some revision and addition in these versions of Bacon and explained the principles of elimination. A principle of elimination helps reject the unnecessary antecedents in a complex situation so that it would be easier to imagine the| cause. These principles of elimination are:
1. Whatever antecedent can be left out without prejudice to the effect can be no part| of the cause
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2. When an antecedent cannot be left out without the consequent disappearing such antecedent must be the cause or a part of the cause.
3. An antecedent and a consequent rising and falling together in numeric concomitance are to be held as cause and effect.
4. Nothing is the cause of a phenomenon, which is known to be cause of a different phenomenon. (Joseph)
Basing on these above mentioned principles of elimination there are five experimental methods which have come to be known as “Mill’s methods of inductive inference”. Mill has formulated five “Canons” or experimental methods for establishing causal connection.
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The experimental methods are named as follows:-
1. The method of Agreement.
2. The method of Difference.
3. The joint method of Agreement and Difference.
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4. The method of Concomitant Variation.
5. The method of Residues.
The different methods make use of the different principles of elimination. For instance the method of Agreement makes use of the first principle of elimination, the method of Difference makes use of the second principle, the method of Concomitant Variation makes use of the third principle and the method of Residues makes use of the fourth principle.
The joint method of Agreement and Difference being a modification of the method of Agreement and Difference makes use of either or both the first principle and the second principle of elimination.