Comparisons help us to take appropriate decisions in daily life, where alternatives are available. The first requirement of comparisons is that alternatives are available. The second is that these things should belong to the same category or class of objects. We do not compare cotton with silk or wool. Thirdly should be some difference among the objects: Finally this difference should be within narrow limits. There is no point in comparing a silk sari of Rs. 300 with one of Rs. 3,000. In common day usage we will say the two are not comparable.

Durkheim used the method of concomitant variations.  Following J.S. Mill’s System of Logic refers appreciatively to the ‘method of concomitant variations’ as the procedure of the comparative method. He calls it ‘the instrument par excellence of sociological research’. For this method to be reliable, it is not necessary that all the variables differing from those which we are comparing to the strictly excluded. The mere parallel between the two phenomena found in a sufficient number and variety of cases is evidence that a possible relationship exists between them. Constant concomitance, according to Durkheim, is a law in itself whether may be the condition of the phenomena excluded from the comparison. When two phenomena vary directly with each other, this relationship must be accepted even when in, certain cases; one of these phenomena should be present without the other. For example, if a plant receives direct sunlight it grows straight but when the same plant is given indirect sunlight it bends towards that light. This shows the concomitant variation of plant growth and its relation to sunlight. Of course we need to reexamine the facts but we must not abandon hastily the results of a methodically conducted demonstration. Concomitant variation can be done at different levels-single society, several societies of the same species or social type, or several distinct social species.

Durkheim wants it to be understood that comparisons can be made of variations of a phenomenon in different parts of a society, of variations of a phenomenon in different societies at a time and of variations of a phenomenon among different societies at different times corresponding to their levels of development. These type of comparison has been exhibited in his study of suicide.

Comparisons within a Society

Durkheim demonstrated the illustration of the first type in his study of Suicide (1897). He compared the different rates of suicides among various sections of the French Society. How is suicide rate distributed among the males and the females, rural and urban populations, persons following Catholic and Protestant faiths, and married and unmarried persons? Data have been processed that way. He has examined the data on differences according to seasons and ‘cosmic’ factors and came to some conclusions other than those already proposed. He found that the rate of suicide had very little to do with the reasons and cosmic factors, such as daytime, evening or night, etc. The rate increased where the social bonds were either too weak (as in the case of egoistic suicide) or too strong (as in the case of altruistic suicide) in a social group.

Comparisons among Different Societies at a Point of Time

The second type of study relates to the examination of the data from different countries of Europe. Durkheim took the case of Germany as a Protestant country, and of Spain as a Catholic country. He found that suicide rates were higher in Germany than in Spain, hence the idea that Protestants commit more suicides than the Catholics. The Jews came still lower. Now we have moved to a new stage in comparative studies. Durkheim studied variations in two phenomena not one: (i) suicide rates and (ii) religions. Variations or change sin the first are accompanied by changes in the second. That is, they vary or change together. This is called concomitant variation, i.e. variation or change occurring together. Thus comparative method tries to see:

•           What are the variations in a phenomenon?
•          Which other variations occur along with those under examination?

This means that comparative method attempts to find out a possible cause for the phenomenon under study.

There can be some problems here. More than two things may change at a time. This was the case in Germany. Catholic faith and low level of economic development were found in Spain. It is the religious difference that is crucial or the level of economic development? Durkheim attempted a solution. He took only one country so the question of difference in the level of economic development did not arise. Then the study was designed thus: Through this design, it is possible to say that the difference in religious faith is accompanied by difference in the social suicide rate; that is, the two vary together. This is concomitant variation. This remains true even when the level of economic development is the same. Keeping this the same, or constant, we get the result that religious faith have an impact on the differential social suicide rates.

Comparisons over a Period of Time

Durkheim clarifies the significance of the time factor in social science studies. His view is that different societies may not be at the same level of development at one point of time. The youth of one cannot be compared with the grown-up stage of another. Thus at one point of time, Spain and Germany were not comparable.