To the contrary, preconceived ideas would pose a threat to scientific method. These could prevent objective reasoning to take place, entice one to tamper with the evidence, cause one to adapt one’s data to suit the occasion or to ignore that which contradicts
Impossible to disagree. So then would not someone like Irenaeus who sought to establish himself as a passionate defender of his branch of Christianity have been susceptible to tamper with evidence? The objective mind is inclined to be cautious and look at motives. He revealed his own by less than subtly saying "true" Christianity has a succession to the Apostles. He forthwith produces one with himself as learning as a child at Polycarp's feet who in turn learned apparently also as a child at Apostle John's feet. To determine the value of this claim we need to see some supporting evidence, but all we find is unsupporting, even contradicting. A forensic scientist would not be impressed with this testimony.
PS. I thought about including some Greek words but then realized how that would come across as trying to impress.