Hello Chris André Stranden,

> I was just wondering: Is the following excerpt from the Buddha's first
> sermon a valid argument for the view that it is possible to realise Nibbana
> through only an intellectual understanding of Dhamma?
>
> "That is what the Blessed One said. The bhikkhus of the group of five were
> glad, and they delighted in his words. Now while this discourse was being
> delivered the hearts of the bhikkhus of the group of five were liberated
> from taints through not clinging.
> And there were then six Arahants, six accomplished ones, in the
> world."

This is not the Buddha's first sermon, this is from Anatta-lakkhana
sutta. Buddha first told them Dhammacakka-pavattana sutta, and Kondanna
gained stream-entry. Then he taught the group of five for several days,
and only then preached Anatta-lakkhana sutta. You can read about it in
Mahavagga of Vinaya-pitaka http://www.sacred-texts.com/bud/sbe13/index.htm .

Its not about 'intellectual understanding'. Buddha had a gift of knowing
other's minds, and of transmitting more than just words.
Probably he had an ability to induce jhana in some of those who listened
to him.

> Or at least - Are such stories a valid argument against the view that it is
> nessecary to achive the jhanas before it is possible to realise Nibbana?

No. Even Sariputta and Moggalana, hearing the teaching of the Buddha
from Assaji, attained Stream-entry. They had to work for several weeks
to achieve Nibbana. Anda they were the foremost in abilities.

Such stories mostly concern the events of Stream-entry (gaining the Eye
of Dhamma, Dhamma-Cakkhu). In other cases, when the hearers achieved
Nibbana, they were already experienced meditators.

Best regards, Dmytro