What kind of incompetent leader would Jesus have to have been to make the sole rule of faith something that 99% of people could not read, let alone afford to hold in their hands for about seventeen hundred years after His death?
Jesus made believing in His teachings the sole rule of faith.
Where better (in this time in which we live) to unquestionably and uncategorically receive His teachings other than in the writings of those who were personally taught by Him ?
What was the purpose of the canonization of the writings of the New Testament ?