the following excerpt is from the beginning of the masechta, does the gemarra that follows define these terms (2 that are 4)? if not could you please help me understand what is meant by them??
1) TWO THAT ARE REALLY FOUR
(a) (Mishnah): There are two primary oaths of Bituy (that one will or will not do something). There are four in all;
(b) There are two primary Yedi'os (awarenesses) of Tum'ah. There are four in all;
(c) There are two primary forms of Yetzi'ah (taking things out) on Shabbos. There are four in all;
(d) There are two primary appearances of Tzara'as. There are four in all. 2) ATONEMENTS FOR TUM'AH
harvey/mechael, lost angeles
The two primary oaths that the Torah specifically mentions are to do something beneficial (e.g. to eat) or to do something harmful (e.g. to fast), both of which are confined to the future. The two that we add are something beneficial of harmful that he already did in the past.
The two primary Yedi'os (awarenesses) of Tum'ah are where the person forgets that he is Tamei and either eats Kodesh or enters the Beis-ha'Mikdash. The two that we add are where he remembers that he is Tamei, but forgets either that he is forbidden to eat Kodesh or that he is forbidden to enter the Mikdash.
The two primary forms of Yetzi'ah (carrying) on Shabbos are where either a person standing in the private domain or a person standing in the public domain carries an object from the private domain to the public domain (which is called 'Hotza'ah'). The two that we add are where the same two people carry from the public domain to the private one (which is called 'Hachnasah').
The two primary appearances of Tzara'as are 'Baheres' and 'Se'es' (two levels of white marks of Tzara'as on the skin), The two that we add are 'Sapachas', which means secondary, and which incorporates a Sapachas of Baheres and a Sapachas of Se'es. To elaborate slightly, 'Baheres' and 'Se'es' are called Avos, and the two Sapachas', Toldos, and each Toldah is slightly less white that its Av.
Wishing you a Kesivah va'Chasimah Tovah.
Eliezer Chrysler. .