Why was the EMH's personhood ever questioned?

Question

In the final season of Voyager, the EMH is forced to undergo a hearing where his personhood (for the purposes of authorship of a holonovel) is questioned. Ultimately, the arbitrator declined to decide on the question of personhood but did grant the EMH the authorship of the holonovel.

I'm curious why there was even a hearing on this? Wasn't Data already considered a sentient being by the Federation? If so, then they had no problem with the notion of an artificial intelligence being sentient.

Was it because the EMH was a "photonic" -- if so then his critique of the oppression of "organics" over "photonics" was quite prescient.

What's also confusing is that in the final season,

"Joe" gets married to an organic (woman no less, since many suspected he was gay)

which seems to indicate that he is viewed as a sentient/sapient being by the Federation.

Answer 1

Unlike Data, whose consciousness seems to be a function of both his unique hardware and his software, the EMH is completely generic. It can be distributed purely as software and only requires a sufficiently powerful computer to run it. In "The Swarm" s3x04 a baseline EMH is used to replace the holomatrix of the ships EMH. We see a copy of the EMH from a backup module (probably created to forestall another breakdown as seen in "the Swarm") in "Living Witness" s4e23.

Where Data was able to gain personhood on his uniqueness the Doctor does not have that attribute. Sure his experience and his growth are unique to him, but if you copied them onto another uninitialized EMH you would have an identical copy of the Doctor, having access to identical experiences. That "perfect cloning" directly separates him from most biological species as, without special intervention (transporter accident or mimetic simbiot), duplicating the original entity is not possible.

Also, unlike Data, since the Doctor's personality is purely implemented in software it is possible to "decompile" him and examine the "logic" behind his behavior. We see Dr. Zimmerman doing some of this in "Life Line" s6e24 as well as Seven of Nine extracting portions of the Doctor's personality (his aesthetics) to make him small enough for transmission. This means that his "creativity" and "individuality" is potentially deterministic. Data and biological being may be deterministic, but their processes are obfuscated behind hardware, whereas the Doctor's is plain to inspect. B'Elanna takes advantage of this fact in "Lineage" s7e12 where she is able to alter the Doctors decisions before he makes them by altering aspects of his program.

Answer 2

I think it's self-evident that declaring Artificial Intelligence A to be sentient (though they probably meant sapient) is not the same as declaring that Artificial Intelligence B is sentient also.

Data and the EMH are entirely separate technologies. As such, the question must be asked for each, individually.

The Doctor also had a further obstacle to overcome: precedence. The EMH was widely-known as a dumb tool, installed on ships throughout the fleet. To suddenly think of this particular instance as something different may not have been all that challenging, but it did require a conscious decision.