11. Why Would The Eye Of Harmony In The Tardis Need A Human Eye To Be Accessed?
To access The Doctor's Tardis, The Master needed a human retinal pattern. Considering that the Eye of Harmony was the power source for a machine intended to be piloted by Time Lords, this seems to be an exceedingly odd security feature. Is this a measure installed by The Doctor to prevent exactly what The Master attempted? This makes sense from the standpoint that The Doctor pretty much always has a spare human laying around that he could use if needed and he does have an aversion to the Time Lords being able to tamper with his Tardis going back to his 3rd Doctor days. But what about when he's traveling alone? Does The Doctor somehow ensure that his eyes are always human even though the rest of his body changes when he regenerates? Or is the simplest answer is that for once The Doctor told the truth and he is half human?