Some of the men of Kekunai once came to R. Joseph and said to him, ‘Send with us a man who might prepare an ‘erub for our town’. ‘Go’, he said to Abaye, ‘and prepare the ‘erub for them but see that there is no outcry against it at the schoolhouse’.
Rabbi Joseph knows this will be a complicated case. The town was once owned by a single person and now is owned by many. They rabbis taught that in such a case there has to be an excluded area. But those who live in that area might not like it! So, he continues to reason:
Proceeding thither he observed that certain houses opened on to the river (with no entrance on land). ‘These’, he said: ‘might serve as the excluded section of the town’.
Changing his mind he said: ‘We learned: NO SINGLE ‘ERUB MAY BE PROVIDED FOR ALL THE TOWN, from which it follows that if it were desired, they could all join in one ‘erub’. I would, however, provide for then, windows, so that if desired they could be joined in the general ‘erub" of the town through those windows’.
Then he said: ‘This is not necessary, since Rabbah b. Abbuha in fact provided separate erubs for each row of alleys throughout all Mahuza on account of the cattle ditches that intervened between the rows, where each row served as the statutory excluded section for the other though these could not join one another in a common ‘erub even if they had wished to do so’.
Then again he said: ‘The two cases are really’ unlike, since there one could if desired prepare the ‘erub by way of roofs while these could not possibly join in one general ‘erub: consequently let us provide for them windows’.
Finally, however, he said: ‘Windows are not necessary either, for Mar b. Pupidetha of Pumbeditha had a store of straw which he set aside for Pumbeditha as the statutory section that was to be excluded’.
‘It is on account of this [group of houses]’. Abaye remarked: ‘that the Master warned me: See that there is no outcry against it at the schoolhouse’.
On another subject Abaye and Rabbi Joseph clash again:
Said Abaye to R. Joseph: ‘Is that ruling of R. Isaac a tradition or a logical deduction?’ — ‘ What’, the other retorted: ‘does this matter to us?’ — ‘Is then’, the first replied. ‘the study of Gemara to be a mere sing-song?’
The sources and reasoning matter. The law is not just ruling handed down, it is deduced! Arguing, even with yourself, is the tradition.