[Avodah] Halachic ramifications of vision strength (from areivim)

[Saul Mashbaum]

The follwing is based on a discussion on Areivim about visible bugs in
brussel sprouts.

RMB
> One of my suggested resolutions is that the definition of "visible bug"
> actually changes with improvements in lighting and eye health. That
> whatever excludes magnification doesn't exclude changes we can make to
> the context that further empowers naked human senses.

R'n CL:
> I find this suggestion difficult.
<snip>
> ....the boundary is very fuzzy.  Some people even in those days
> had better eyesight than others.  Does it vary from person to person?  Can
> Rachel eat a fruit checked by Rachel, but not by Leah, and does Leah have to
> check that Rachel has at least as good eyesight as she does before she eats
> in her house?  What about husband and wife?

MYG:
> .... I do have one situation in which the halachah changes based
> on vision - the Biur Halachah in Siman 79 (DH Oy SheHu Suma) says that a
> person has to distance himself from Tzoah when saying Shema at night based
> on how well he sees during the day. One who sees farther will have to make
> sure he's farther away.

Many dinim are dependent on vision, and one may well inquire exactly
whose vision we are talking about in determining the halacha.

I'll give some examples from the mechaber in SA OCh:

58:1 The time of Kriat Shma in the morning is from the time one is able
to recognize a slight acquaintance from the distance of 4 amot.

293:2 One should be careful not to do m'lacha Saturday night until 3
small stars are seen (ie, can be seen SM).

688:2 [The megilla is read on the 15th] also in villages which are seen
(ie, can be seen SM) from walled cities.

The first case seems to be according to the individual, based on each
person's eyesight. Thus, one could have a situation in which at a certain
time,a sharp-eyed person could say Kriat Shma, while his dim-sighted
friend could not.

In the second two cases, the mechaber uses the passive voice, and we have
to determine if we are talking about things see-able by each individual
(the halacha differing from person to person) or if the halacha applies
to everyone simultaneously, based on average vision, the best vision,
or the weakest normal vision.

Similarly, the poskim say that the requirement for square tefillin
does not exclude tefillin which are not square based on microscopic
measurement; rather, tefillin which appear square based on examination
by normal eyesight are kosher. Here too, if one person's eyesight is
better that another's, does that mean that the same set of tefillin
could be kosher for one person, and pasul for another? Or, perhaps,
if the tefillin are square according to average vision, they are kosher
for everyone.

One last case, outside of the SA: Maaser sheni may be eaten outside of
Yerushalayim in places from which Yerushalayim can be seen. Seen by whom?
The individual eating the maaser sheni? Most people? Perhaps maaser sheni
may be eaten even in places from which only people with very good vision
can see Yerushalayim, or perhaps only from places which even people with
poor vision can see Yerushalayim.

Tzarich iyyun.

Saul Mashbaum