1 Corinthians 11:19

'For there must be ('it is necessary for there to be') also factions among you, that those who are approved ('have stood the test') may be made manifest among you.'

He now gives a further reason why he 'partly believes it', and that is the necessity of it. This necessity arises either because he knows them well and views the Corinthians as being such that it is inevitable, or possibly because he knew that Jesus Himself had forecast that there would be factions and divisions, even within households, because of His name (Matthew 10:34; Matthew 24:9). And the divine result of these would be that those who were truly His would by them be revealed.

So while on the one hand he finds it difficult to believe that the church of Jesus Christ could behave in this way ('I partly believe it'), on the other he is sadly aware that this is not only possible but is forecast as something that is eventually coming. Thus he senses, knowing their propensities, that it may well be that the Corinthians are already caught up in it. There is a guarded warning here for them. Let them beware lest these factions demonstrate that they are not really of the truth.