Dear Alex,
Thank you, but I’m not sure that this formulation counts as modus tollens. It is usually stated in the form: if a, then b. Not b, therefore not a.
Thus:
If there would have been smoke on the mountain, there would have been fire there. But there is no smoke, therefore ...
Best wishes,
Eli


Sent from my iPad

On 01.07.2021, at 13:49, Alex Watson <alex.watson@ashoka.edu.in> wrote:

Dear Eli

Let's take as an example of modus tollens:

Major premise: wherever there is smoke there is fire
Minor premise: there is no fire on the mountain
Conclusion: there is no smoke on the mountain

I don't think Indian logicians would see this as a prasaṅga
nor western philosophers as a case of reductio ad absurdum,
as it doesn't conclude something absurd or undesirable, 
therefore we are not compelled to reject one of the premises.

Yours Alex

--
Alex Watson
Professor of Indian Philosophy
Ashoka University

> Dear friends,
I have been wondering about something that is perhaps only tangent to 
the discussion. Can one distinguish between reductio ad absurdum 
(prasanga) and modus tollens (also prasanga?) in the Indian tradition? 
I am not sure that the distinction between the two is clear in the 
Western tradition either.
With best wishes,
Eli