In short, by illustrating the lack of applicability of scientific evidence to some aspects, they attempt to carve out space where evidence should not be applicable, and finally put all their superstitions in that space, insulating it from demands of evidence.
Prof Gadagkar addresses this specific criticism of scientific method in his article on scientific temper. He says:
I am a Professor at the Indian Institute of Science. I have a Ph.D. in Science. I teach courses in science. I was the President of the Indian National Science Academy. So, by all accounts I am a scientist. But is that always true? Am I a scientist 24/7? Do I use the scientific methods for everything? The answer is a clear No. I do not use the scientific method when I decide what music I would like to listen to, when I decide which restaurant I should go for dinner or what colour shirt I should wear.On the instances when the scientific method is necessary, Prof Gadagkar writes
If we want to know whether smoking cigarettes increases the risk of cancer, we must use the scientific method, if we want to decide whether a little bit of red wine actually reduces the risk of heart disease, we must use the scientific method, if we want to decide to learn how to put a space craft on the moon, we need the scientific method and if we have to decide whether or not Indians practiced inter-planetary travel thousands of years ago, we must use the scientific method. It is perfectly alright for me to say I like Hindustani music more than Carnatik music without scientifically justifying it, but it is not alright for me to say that genetically modified (GM) crops are bad for us or indeed to say that GM crops are good for us.
We can expand Prof. Gadagkar's argument and say that the relevance of scientific method to a problem depends on three factors - the nature of the claim, the stakes involved, constraints of collecting evidence. The method of verification depends on these three factors.
1. Nature of the claim: The question requiring scientific rigour should be the one relating to what we call the material world and the concerned laws, especially the ones making causal claims. For instance, X as the cause of Y phenomenon in the material world (Apples fall due to gravity, Medicine cures ulcer) concerns the material world making causal claims and hence are in the domain of science. On the other hand, it is not needed to choose Carnatic Music over Hindustani or a blue shirt over a black shirt. These are just matters of taste that do not make any causational claims.
2. Stakes involved: The necessity to verify and the amount of rigour required to substantiate the claim also depends on the stakes involved.
For instance, if I ask the security guard for the directions to the washroom in a mall, I don't need to verify his answer. I just follow his directions. The stakes involved are low. In the worse case, I might not find or I get delayed.
But, if we are on a long journey without google maps, we usually cross-check the directions by asking multiple people. It's because the stakes are little higher here as we don't want to waste time and energy in getting lost!
It means that the demands of rigour increase with the stakes involved.
3. Constraints of collecting evidence: Advocates of reason and evidence only demand to arrive at the best possible conclusions with the available evidence, and revising the conclusions in case if evidence to the contrary emerges.
Real life demands decisions within a particular time frame. In such cases, people make decisions with the best possible evidence at that point in time, considering the constraints in collecting evidence. The decisions made on such limited evidence doesn't in any sense contradict the notion of "reason-based decision" as long as the best possible is used and interpreted in an appropriate manner.
For instance, if the above example of cross-checking security guard's instructions in the mall, it is enough if you cross-check with one or two persons. You cannot be held accountable for not cross-checking with the building approval plan.
Similarly, the people in the Bigg Boss House make decisions based on the limited access to evidence. They cannot be held accountable for not going through the recorded tapes before making a decision.
Method of verification
1. The evidence is not necessary for every decision of life - liking Hindustani music or Carnatic music. The necessity of evidence and the rigour depend on the nature of the question and the stakes involved.
2. There are different methods of verifying claims using reason. Usage of different methods for different contexts is not contradictory to the advocacy of reason based thinking.
3. Extraordinary claims require extraordinary evidence. Causal claims about the phenomena of the material world require the highest rigour of evidence.
4. One should make decisions based on the best possible evidence, using the best possible methods, as per the nature of the question and the stakes involved.