They say: If we validate the sale of the mother but not the fetus, it becomes like selling a pregnant animal while excluding her fetus. It has already been stated that, according to the school, selling a pregnant animal while excluding her fetus is invalid. But based on the view we have regarded as stronger—that if a person sells a pregnant animal and excludes the fetus, the sale is valid—it is valid here as well.

His statement, “But if ascertaining it is not impossible, it is valid with respect to the known item in its proportionate share,” means: if ascertaining the unknown item is not impossible, the sale is valid with respect to the known item in its proportionate share. This is because the price can be apportioned between the known and the unknown items, thereby determining the price of the known item.

An example is where he sells him the car presently here and another car that is absent, both cars for ten thousand. The other car, which is absent, is unknown. Thus, the sale is valid with respect to the present car, but not with respect to the absent car, since it is unknown.

How is the price apportioned?

We estimate the value of the car before us. If its value is ten, while the value of the other is five, we divide the price into thirds: two-thirds for the present car and one-third for the absent car. Thus, the price is apportioned between the known present item and the unknown absent item. The price of the known present item is taken, while the other portion is waived, because the sale concerning it was not valid.

Thus, selling a known item together with an unknown item falls into two categories:

The first: where ascertaining the unknown item is impossible.

The second: where it is not impossible.

If ascertaining it is impossible, the sale is invalid unless a price is assigned to each of them,