Q&A: A Fortiori Inference
A Fortiori Inference
Question
I once heard in the name of Rabbi Hillel Zaks of blessed memory that there are various a fortiori arguments that simply should not be made, and he gave these examples:
1. If fish, which are not eaten with a spoon, are eaten with a fork, then soup, which is eaten with a spoon, should all the more so be eaten with a fork.
2. If my pocket, which you are forbidden to put your hand into, I am allowed to put my hand into, then your pocket, which you are allowed to put your hand into, should all the more so be permitted for me to put my hand into.
What exactly is the flaw here? After all, it seems very similar to many a fortiori arguments that appear in the Talmudic text.
Thanks, and sorry for the bother.
Answer
You need Rabbi Hillel Zaks for this? Without his saying it, would you have made such an a fortiori argument? There is plain common sense, and every person understands how to use it.
This is not similar to a Talmudic a fortiori argument, and I have already discussed this in several places. An a fortiori argument assumes that the laws belong to the same field of meaning, and only for that reason can such an inference be made. The writers on the interpretive rules already bring an a fortiori argument to obligate a doorpost in tzitzit: just as a four-cornered garment, which is exempt from mezuzah, is obligated in tzitzit, then a doorpost, which is obligated in mezuzah, should all the more so be obligated in tzitzit.
It seems to me that I wrote about this in Midah Tovah 5765–5766, on the Torah portion of Shemini:
https://drive.google.com/drive/folders/0BwJAdMjYRm7IRmM4RGd0dG9zWU0