Going by what we see in the book, Ginger doesn't seem to have originally been "in" on the plan to claim that Aslan and Tash are one. When Shift first declares "Tash and Aslan are only two different names for you know Who.... Tash is Aslan: Aslan is Tash," we're told that all the Talking Beasts looked heartbreakingly sad, except for one, the ginger cat:

"Excuse me," said the Cat very politely, "But this interests me. Does your friend from Calormen say the same?"

"Assuredly," said the Calormene. "The enlightened Ape — Man, I mean — is in the right. Aslan means neither less nor more than Tash."

"Especially, Aslan means no more than Tash?" suggested the Cat.

"No more at all," said the Calormene, looking the cat straight in the face.

"Is that good enough for you, Ginger?" said the Ape.

"Oh certainly," said Ginger coolly. "Thank you very much. I only wanted to be quite clear. I think I am beginning to understand." (pp. 34-36 in the Puffin edition)

That's the first time we meet Ginger in the story, though of course we're seeing him through Tirian's eyes. We could take it that he's a deliberate plant — already an ally of Shift and Rishda and just pretending to be one of the crowd so that he can declare his support at this critical moment. But from the way that scene is written, it implies he genuinely hasn't heard of this concept of "Tashlan" before and he's just at this moment realising that this is something he can turn to his own advantage. That's confirmed somewhat later in the story when Poggin the dwarf reports the conversation he heard later that same night between Ginger and Rishda:

"Noble Tarkaan," said the Cat... "I just wanted to know exactly what we both meant today about Aslan meaning no more than Tash." "Doubtless, most sagacious of cats," says the other, "you have perceived my meaning." "You mean," says Ginger, "that there's no such person as either." "All who are enlightened know that," says the Tarkaan. "Then we can understand one another," purrs the Cat. (p. 74)

So it sounds very much as though "Tashlan" is a concept that Rishda made up (Shift clearly isn't clever enough to have thought of that!) in order to persuade the Narnian beasts that the Calormenes' takeover of Narnia is divinely ordained. Ginger obviously already didn't believe in either Aslan or Tash, but he latches onto what Rishda is doing and decides to get on board — as he shows in his subsequent remarks to Rishda, he counts himself among "those who care neither for Tash nor Aslan but have only an eye to their own profit and such reward as The Tisroc may give them when Narnia is a Calormene province" (p. 75). As far as I can see, then, Rishda is the mastermind behind the plot.

It's been my impression that it was Rishda who came up with "Tashlan". It makes me wonder if he was trying to come up with something impressive... being an upper class Tarkaan and all. He and Shift have been saying "Tashlan" at the midnight meeting, until the battle line is drawn. Tirian says,

"To my side all true Narnians, or will you wait until your new masters kill you all one by one!"

Then Rishda says,

"To me, all loyal Narnians, lest the wrath of Tashlan fall upon you!"

Then Shift is hurled into the stable... the Calormenes see a blinding green light and hear sound of squawking of a monstrous bird... Rishda stopped saying "Tashlan" after that. It makes me wonder after that moment, he forgot about he was saying. So it would seem to me that Rishda was trying to come up with something impressive by saying "Tashlan".

Posted by: @jasminetarkheena

Rishda stopped saying "Tashlan" after that. It makes me wonder after that moment, he forgot about he was saying. So it would seem to me that Rishda was trying to come up with something impressive by saying "Tashlan".

Going by what's in the book, it looks very much like "Tashlan" was a concept made up by Rishda to justify (to the Narnians) the Calormenes' conquest of Narnia — when the Talking Beasts start asking, quite rightly, why Aslan would give Narnia to the Calormenes when they worship a different god, Tash. It doesn't seem to be a matter of him merely sounding impressive; it's a clever political ploy from an astute and manipulative commander. Rishda himself makes clear, in private, that he doesn't believe in Tash or Aslan at all, let alone in "Tashlan". He just wants the Narnian creatures to be terrified into believing that the Calormenes have taken over Narnia by divine decree.

The point where Rishda stops saying "Tashlan" is the point where, as you've mentioned, everyone sees the blinding light and hears the sounds like a monstrous bird after Shift is thrown into the stable. Farsight the Eagle, at that moment, sees Rishda's face and realises that the Tarkaan is "just as surprised, and nearly as frightened, as everyone else":

"There goes one," thought Farsight, "who has called on gods he does not believe in. How will it be with him if they have really come?" (p. 106)

That, basically, is the moment where Rishda starts to realise that the god he's been denying is, in fact, real and powerful and obviously dangerous. And going by the "monstrous bird" sounds, the god in question can only be the bird-headed Tash and not the Lion Aslan. It makes sense that at this point he drops all the pretence of "Tashlan" and starts referring to Tash again.

We see this in the next chapter, when Rishda has the Dwarfs thrown into the stable and calls it "the shrine of Tash" and declares "These also are for thy burnt offering, Lord Tash" — and his soldiers are also shouting Tash's name, with "no nonsense about 'Tashlan' now" (p. 117). Whether or not they believed in Tash before this, they certainly do now — and Rishda has just had to revise his own atheistic worldview completely and is apparently now trying to ingratiate himself with the god he didn't believe in until that night. Not that it does him any good in the end!

posted by: @courtenay

and Rishda has just had to revise his own atheistic worldview completely and is apparently now trying to ingratiate himself with the god he didn't believe in until that night. Not that it does him any good in the end!

Of course it didn't. Tash shows up right before Rishda in the stable after he and King Tirian are hurled in there (well, sort of... Tirian puts himself in there, taking Rishda with him). Seeing the illustration of Tash by Pauline Baynes... oh, I wasn't traumatized by it, since I was about ten when I was introduced to the series. When I saw that for the first time, I was like, "What is that thing?"

From a political aspect, Rishda, being a Tarkaan and a captain, seemed to have too much power. He used manipulation to take over Narnia. Politics tend to have too much power, and be manipulative. Oh, it has happened throughout history, and history has a way to repeat itself. Same for Narnia history, there had been political leaders in Narnia who had too much power; they are manipulative each in their own way. Manipulation is seen almost throughout the series.

I suppose, from a religious aspect, Rishda could be equivalent to those had been raised in a certain religion (Christianity, Islam, Buddhism, etc), and might say the name without believing in them. For instance, someone who had been raised in a Christian home might say the name of Jesus, and not believe in Him. Same for someone who had been raised a Muslim; that person might say the name of Allah and not believe in him. So that could be the same idea there.

I also thought about Ginger being involved with Tashlan because in the book Poggin says-

"Curst, curst cleverness!" said Poggin. "I'll be sworn that this new lie is of Ginger's making."

Since Ginger made up stories about Aslan, like how he swallowed up King Tirian whole (which wasn't true, of course). So during the time that Shift got all the oranges and bananas and drinking, it would have seem that Rishda and Ginger have been working closely together.

I recently had a Sunday School lesson in our Narnia series that Rishda called on gods he doesn't believe in. It's almost like praying when it's not sincere.

As for the blending of Aslan and Tash, "Tashlan", well we might established that Rishda was the one who came up with it. Then Ginger could have been involved as well. Since Poggin says in the book,

“Cursed, cursed cleverness!” said Poggin. “I’ll be sworn that this new lie is of Ginger’s making.”

Since Ginger was known to come up with new lies about Aslan, it might be safe to say that he came up with the new lie about "Tashlan" and had Shift do the talking. Most likely Rishda and Ginger came up with the new plot together- Ginger the new lie and Rishda "Tashlan". And Shift had to do it all in one.

Posted by: @jasmine_tarkheena

Since Ginger was known to come up with new lies about Aslan, it might be safe to say that he came up with the new lie about "Tashlan" and had Shift do the talking. Most likely Rishda and Ginger came up with the new plot together- Ginger the new lie and Rishda "Tashlan". And Shift had to do it all in one.

This was covered earlier in this discussion thread, though — when Shift first tells the Narnian beasts that Tash and Aslan are the same, Ginger is the one who speaks up and shows interest in this idea as if it's new to him. It could be, of course, that he is already in on the plot and has been deliberately planted in the crowd of Talking Beasts to show approval of "Tashlan" at that crucial moment when all the other animals are responding with disbelief and shock.

But his later conversation with Rishda, as reported by Poggin, makes it clear that Ginger DIDN'T already have this notion of "Tashlan" before Shift introduced it. He asks what Rishda meant by the concept and confirms that Rishda, like himself, doesn't actually believe in either Aslan OR Tash and is solely interested in using the invented concept of "Tashlan" to gain power over the Narnians. As I quoted earlier, this is Poggin's report of their conversation:

"Noble Tarkaan," said the Cat... "I just wanted to know exactly what we both meant today about Aslan meaning no more than Tash." "Doubtless, most sagacious of cats," says the other, "you have perceived my meaning." "You mean," says Ginger, "that there's no such person as either." "All who are enlightened know that," says the Tarkaan. "Then we can understand one another," purrs the Cat.

If Ginger had been in league with Rishda from the start, and especially if he had been instrumental in coming up with "Tashlan" — the concept or the name or both — they couldn't have been having that conversation at this point, because there would be no way that Ginger could be uncertain that they both meant the same thing and had the same ambitions. They would have had to discuss those things before getting Shift to declare that Aslan and Tash are one, and this conversation clearly takes place after that happened.

So the only logical conclusion is that Ginger was NOT part of the "Tashlan" plot before that night, but as soon as Rishda discovered that the Cat was on the same page with him (so to speak), he was happy to include Ginger as an ally and get him to spread further lies to his fellow Talking Beasts, as the rest of their conversation soon shows.

@courtenay 

It's hard to know whether Ginger was part of the plot from the start or as soon as Shift said that Aslan and Tash were one and the same, he decided to join in.

Some might argue that in the "Tashlan" conspiracy, Shift uses brains, Ginger uses words, and Rishda uses brute force.

One might recall that Shift was a manipulator himself, since he manipulated Puzzle into pretending to be Aslan. Then it comes to a point that he himself gets manipulated by Ginger and Rishda. It's poetic justice there. Just as Puzzle had to do what Shift told him, in turn, Shift had to do what Ginger and Rishda tell him.

Posted by: @jasmine_tarkheena

It's hard to know whether Ginger was part of the plot from the start or as soon as Shift said that Aslan and Tash were one and the same, he decided to join in.

Not really, as far as I can see from the book. If Ginger had been part of the plot from the start, there's no way he would have been confirming with Rishda what he meant by Aslan meaning "no more than Tash" AFTER Shift and Rishda made their first public declarations about "Tashlan". If Ginger had been in league with them before that, he would have already known what was behind the "Tashlan" ploy, especially if he had helped them to come up with it. I can only conclude, from the text itself, that Ginger wasn't part of the plot until that night, but as soon as Rishda confirmed that Ginger was on his side, he started giving him (Ginger) work to do as well.