The Talmud relates the opinion of R. Meir that in a situation of indeterminate impurity of liquids, the assumption is toward impurity if the focus is the status of the liquid itself. If, however, the question is concerning the liquid conveying impurity onto another object, the presumption is toward purity. As Rashi explains, this is a function of the different rules for safek (indeterminate situations) in biblical and rabbinic law. In the first case, where a biblical law is involved, a safek is treated stringently (safek d’orayta l’chumra); in the second, apparently a rabbinic possibility of impurity is present, and thus the matter is treated leniently (“safek d’rabanan l’kula”).

The Birkat Avraham finds this explanation troubling. The rule regarding a safek of impurity is that in a reshut hayachid, the assumption is impurity. The existence of such a notion has the effect of granting a definite status of impurity in that situation. If so, what room is there to utilize “safek d’rabanan l’kula”, once the safek has essentially been neutralized?

The Birkat Avraham suggests that the issue may turn on the explanation of the concept of “safek d’rabanan l’kula”. The Shev Shmat’ta (I, 3) cites the position of the Tashbetz in explanation of this idea: the Rabbis, when they created their enactments, only addressed definite situations. Thus, when a case is indeterminate, it was never prohibited in any sense by the enactment.

If one adopts this explanation, the above statement is easier to reconcile: there is simply no impurity present at all, in absence of a rabbinic enactment; thus, the rule of “safek tumah b’rishut hayachid” does not come into play.

However, the Shev Shmat’ta himself does not accept the explanation of the Tashbetz, and prefers another theory. The view of the Rambam is that the position of stringency in a case of biblical safek is in itself a rabbinical notion; on a biblical level, every safek is permitted. Accordingly, the Rabbis imposed this stringency only on biblical law, and not their own laws. The implication of such a position would be that the impurity exists, but nonetheless allows for leniency. If so, the rule of “safek tumah b’rishut hayachid” should come into effect. This view makes the above statement about liquids more difficult to explain, and the Birkat Avraham leaves it as an unresolved question.