A thing or two I learned about syllogism and logical reasoning:

If I own Final Fantasy 7 (and all related games/movies/stories), then Aeris wouldn't have died, Sephiroth and Rufus would have been playable characters, and the Cetra's history would be told in detail.

But Aeris dies, Sephiroth and Rufus are NPCs, and none of the old Cetra characters appear as main characters.

Therefore, I don't own Final Fantasy 7 (and all related games/movies/stories).

Professor Gast's Journal

Day 1
Arrived at Icicle Village. Currently in the inn. Summer fast approaching – but then, it wouldn't matter anyway: temperature still remains at -2 degrees centigrade, and summer would only bring about approximately 5 degrees.
Hojo and Shinra are still looking for me. The JENOVA project – I can't stomach the direction Hojo took. Perhaps it is for the "greater good" as he acclaims, but the child – Sephiroth they named him – was not given a choice. For the greater good, they all said.
But – sacrificing one's happiness, one's right, for the greater good?
This process, however, also works inversely in society. In Midgar, for instance: the common good is compromised for the benefit of an oligarchy… but it is the same oligarchy now that claims that one's being be experimented upon for the common good.
Hah. This entire obsession with the Cetra…
Woe to the day I found that JENOVA specimen!

Day 4
Managed to mingle with the locals. Very friendly – they gave me a space to live in for a while. They also speak of a hot spring with curative powers in the middle of the snowy wastelands outside, among many other interesting tales. These would seem to be naught but fairytales told to children, if only the people are not convinced of their authenticity.

Day 8
One of the locals invited me to tour the hot spring. Snowboarding. This being the most credible of the tales (perhaps a large Mako concentration gives the spring its curative powers) I decided to investigate the site. Who knows? I might even be able to procure samples and synthesize a tonic for the villagers.

Day 9
Guide tells me I reached the outskirts. Must mark trail. -4 degrees. Guide says it's normal.
I'll carry on.

Day 10
Lost! The fog – can't see last marker.
Cold. Temperature dropping steadily. Blizzard.
Must find spring. It's too cold.

Day 11
Cold. Too cold. My senses. Numb. -18 degrees.
Must go on.

Day 12
I am lost.

Day 16
Woke up in a small but cozy house, fire crackling merrily. In that house lives a woman. She had long brown hair, green eyes. Nursed me back to health for 3 to 4 days, it seems. I don't know how. There was no sophisticated medical apparatus.
Her name was Ifalna.
People say that she's a Cetra. The last one living.
Ridiculous.

Day 18
So she is a Cetra? Interesting.
At first, she wasn't too willing to set an interview with a Shinra scientist (such as I am), the company being unpopular for its using Mako energy, which – as theorists in Cosmo Canyon hold – denudes the planet's life source. However, I managed to convince her that what I'm doing is merely a freelance research about the Cetra.
She agrees to a recorded interview tomorrow morning.

The following takes place in Professor Gast's lodging the next day
Year XXXX, Month XX, Day XX, 10:42 AM

Gast: So, Ifalna, people say you are the last living Cetra. But, in the first place, what is a Cetra, precisely? What makes them different, from, say, Wutaians or Corelians?

Ifalna: The Cetra were a nomadic race who lived in the Planet more than 2000 years ago. They had the capability to hear the Planet's voice and… and… by modern-day conventions, use magic.

Gast: Hear the Planet's voice?

Ifalna: Yes, Professor. I can't explain it very well, but it's like having a conversation with the Planet, getting to know its joys, its pains…

Gast: So the Cetra can hear and speak with the Planet?

Ifalna: Yes, Professor.

Gast: And you are a Cetra?

Ifalna: Yes.

Gast: I see. Just curious, though – about five years ago, our science team has managed to unearth a Cetra, which we have called JENOVA. Do you happen to know anything about this ancient Cetra?

Ifalna: ...!!!

Gast: Ifalna?! Is something the matter?

Ifalna: That… thing… you excavated… was NOT… a Cetra.

Gast: ...?! What do you mean?!

Ifalna: It was… him. The calamity from the sky. Heaven's dark harbinger.

Gast: I… still do not get you… Ifalna… shall we… carry on with this? You don't look… fine…

Ifalna: It's… alright, Professor… I… I can tell… the full tale…