Uddaalak's Teachings
Adapted from   Shrisha Rao's "The Superstitions"

If Uddaalak really wanted to teach Shwetketu 'Tat Twam Asi', there would be no need to the above three statements from Uddaalak. In  addition, if Uddaalak's intention was to teach 'Tat Twam Asi' to Shwetketu, to break his arrogance, why would he not teach him directly 'Tat Twam Asi', instead of teaching him 'Tat Twam Asi', and expecting the son to understand it as 'Tat Twam Asi'. Only one who wants to move the data point to the curve he has drawn would think so and there is no such line drawn by by Uddaalak here. In addition, there was no need for Uddaalak to doubt the sincerity of Shwetketu, to learn that, knowledge for which the son voluntarily submitted to. With the submission, there is no more arrogance. As the context indicates, the stage was set for teaching 'tat twam asi'.

The Vedaant curve is drawn by Ved Vyaas. If you stay close to Ved Vyaas' teachings, there is no need to move any data points. Pramaan (measures) do not contradict with one another. You want to be nice to Shwetketu. Hence you have made the assumption that Chhaandogya did not teach 'Tat Twam Asi'. Did you know that the same Shwetketu also shows up elsewhere? Do you know his behavior there?. I suggest you study them before you start taking sides.

'Aitad Aatmya midam sarvam tat satyam sa Aatmaatatwam asi Shwetketo bhooya Eva....." This sentence, when chanted 'Tat Twam Asi' and 'tat twam asi' would sound the same. Both are grammatically perfect. The only question is, what do you make out of either one?

Pratyaksh has already shown you are not "That". Geetaa and Sootra have already taught us, you can't be "That". "ananya prokte gatiratra nasti" of the Kathopanishad, has denied identity between Jeevaatmaa and Paramaatmaa in no uncertain terms.

Now you are forcing Uddaalak to go against every other known Pramaan. Just to hold onto your 'tat twam asi'?. What for?. Do you know what else Uddaalak asks Shwetketu to do?. He asks him to live on water for 15 days without eating any other food, >and then come back to him and chant what he has learnt in Gurukul. poor Shwetketu is unable to recall any of the Ved Mantra, that he thought he had mastered and hence has become arrogant.

"na vai maa pratibhaanti bho" iti | After this failure to recall memory, Shwetketu is allowed to eat and then only he is able to chant them again.

If you want to teach your son that he himself is Brahm, then, why make him starve for 15 days first?. Any explanations?

"You are "That", but only if you don't skip many days of eating food. Is this what we should learn from Chhaandogya Upanishad? If you skip food, then you are hopelessly lost in your abilities to recall anything. In the context of this episode, 'Tat Twam Asi' can only be talking about Shwetketu's dependencies.

Whatever happened to 'That thou art' here? So, Uddaalak's actual actions do appear to show that he is out to teach his son a lesson about his own dependencies on items such as solid food. According to you, that lesson is "That thou art" in spite of the fact that Uddaalak himself never claimed "I am That".

Where did you learn that Vaidik God also gets into forgetful states once in a while?. If not, where is the question of "That thou art"? The Brahm in Dwait Maarg refuses to accept "That thou art" even after a thorough study of Ved and Geetaa and Sootra.

Where did Ved teach anyone that Brahm refuses himself in some and accepts himself in some others? 'That thou art' is making a joke out of Ved and Upanishad.

Nachiketaa who is Shwetketu's brother, is a Uttamaadhikaaree for Gyaan. Study Kathopanishad. Yam somehow forgot to teach him "That thou art" - the greatest teaching on earth, where as, his brother Shwetketu who has no Vairaagya, no Guru Bhakti on his Gurukul teachers, and has to be made to starve for 15 days to get the point across, such a Shwetketu is your best candidate for teaching "That thou art"?

A million other problems show up if you follow 'That thou art'. Our knowledge from third of chapter of Chhaandogya Upanishad will start contradicting our knowledge from sixth chapter of the same. Our knowledge from Geetaa will start contradicting our knowledge from Chhaandogya. The Sootra teachings will start contradicting our knowledge from Chhaandogya.

One more problem.
Gyaanaasi maam? Gyaanaasi maam iti | "tasya yaavanna vaak manasi sampadyate, manah praane, praanah tejasi, tejah parasyaam devataayaam taavat Jaanaati"

Sick person on his death bed example. His relatives sitting around him, keep asking "do you know who I am?". The sick person is able to recognize only till the other Devataa are operating in him, otherwise not. How does this fit into 'tat twam asi'?

Observe the key word 'Devataayaam'. Why is Uddaalak teaching Shwetketu about all these other Devataa? Have you ever thought about it?

"atha yadaasya vaak manasi sampadyate | manah praane, praanah tejasi, taajah parasyaam devataayaam atha na jaanaati"

You are so hopelessly dependent on these Devataa, however 'You are Brahm' !! Does this even make any sense at all?

In the context of the sick person episode, 'tat twam asi' can only mean, 'You are so dependent on God'. How can you be arrogant?

In spite of 'tat twam asi' no one else has been able to show Vishwaroop, that Brahm of the Geetaa had shown to Arjun. In spite of 'tat twam asi' claims, no one knows why the Brahm that you always were, have shown up like this?

In other words, in your view, it is possible that Vaidik Brahm also can get into hopeless states with all kinds of contradictory knowledge. In your view, it is possible that Brahm refuses to realize that he himself is Brahm, in people like Arjun, whereas an ordinary Vedaant drop-out has already realized it.

As I said, we don't have an issue regarding 'tat twam asi' or 'Tat Twam Asi' word split. What do you make out of it, in the context of the Upanishad is the million dollar question. So, later on thinkers had to restore consistency in knowledge that was lost because of 'tat twam asi' given by A-Dwait s "That thou art".