1) The word "ha'Beged" suggests that the Beged is intact. The word "Beged" without the "Ha" suggests that the Beged is no longer intact. The difference is that the extra "Ha" at the beginning means "the," so this gives the Beged an additional importance. (In English we call this "the definite article" which gives an item more importance.)

2) Therefore, since the Mishnah says "Petilat ha'Beged," this means that the wick has been made by folding the Beged but the Beged is still intact. (Had the Mishnah said "Petilah Shel Beged" this would have meant that the material has been detached from the Beged and then folded to make a wick.)

3) We see that Rebbi Akiva changed his mind because the Mishnah states "ha'Beged," which means that the Beged still has some importance, but nevertheless Rebbi Akiva maintains it is Tahor. This fits with Rebbi Yehoshua's opinion, who maintains that even a Beged which still possesses some importance (since it has not yet been thrown into the garbage) is nevertheless Tahor.

Dovid Bloom