Shabbos 69 - Tefillin On Shabbos

The דובב מישרים [The Chebiner Rov] is one of those sfarim that m'darf lernen - we must learn.

He was asked [ח"א סי' יח] about the gemara that says that if a person is stuck in the desert and doesn't know when shabbos is, he should keep six days and commemorate the seventh by making kiddush and havdala עיי"ש. The question is - Should he lay tefillin with a bracha on the seventh day as well? Apparently - he shouldn't because it would be תרתי דסתרי - an inherent contradiction. First he wears tefillin with a bracha and then he makes kiddush? Modna [strange]. [For an interesting article on תרתי דסתרי by someone who is unfortunately in the papers for yichee things, see the קול התורה journal נב page קנה and on.] 

Strange or not strange, the Chebiner says the we see that we make a bracha in the case of a sfeik sfeika and here we have a רוב [because most days are weekdays] that would mandate a bracha. [Those who follow my Shev Shamtsa articles know that according to many - ספק ספיקא is מטעם רוב].

The Maharam Mintz proves that we make a bracha on a רוב from the gemara in Yevamos [121] that says that one can take a שבועה based on a רוב so הוא הדין to make a bracha. [Rav Genechovski has a nice discussion of this topic in his בני ראם. Please learn it:)].

Another svara to make a bracha would be that don't wear tfillin because shabbos is itself an אות so we don't need another אות of tfillin. But this fellow stuck in the desert IS doing melacha [כדי פרנסתו] and ממילא he should make a bracha on his tfillin.

See the sefer זרע ברך עמ' רלו רלח and דף על דף for more...