Contextualism: An argument in search of a conclusion

"You know you are a moderately competent art history graduate student. You are visiting a 15th century Italian church Professor Takayama, the world's foremost expert in Fra Angelico. You see a painting that you think is quite definitely not by Fra Angelico. Professor Takayama points to it and says: 'I am quite certain this is by Fra Angelico.' You conclude, on the authority of the great Takayama, that the painting must indeed be by Fra Angelico. Then Professor Takayama turns to you and asks: 'Do you agree?' You respond, quite honestly: 'Yes, quite certainly.'"