In Lord of the Flies, since Percival is inarticulate, what does this fact demonstrate about the boy's experience on the island?

Since the use of the word
inarticulate is in the question, perhaps the reference is made to
Chapter Five of Lord of the Flies in which the assembly is held and
Percival Wemys Madison is called upon to testify about sighting the beast.  When he is
asked his name, Percival can no longer remember his phone
number:

As if
this information was rooted far down in the springs of sorrow, the littlun wept....At
first he was a silent effigy of sorrow; but then the lamentation rose out of him, loud
and sustained as the
conch.

His crying reminds the
others of their sorrows; they weep, too. When Jack asks him about the beast, Percival
yawns and staggers. As Jack grabs him, he sags.  Finally Percival tells Jack that the
Beast comes from the sea.  It is Simon who attempts to explain that the beast may be
real: "maybe it's only us."  When Piggy shouts "Nuts!" Simon then becomes
inarticulate and his
effort

falls
about him in ruins; the laughter beat him cruely and he shrank away defenseless to his
seat.

Later, as Ralph cries
desperately,

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"If only they could get a message to us....If
only they could send us something grownup...a sign or
something.

Then, a thin wail
out of darkness chills them, sending them grabbing for each
other.

...the
wail rose, remote and uneartly, and turned to an
inarticulate gibbering. Percival Wemys Madison, of the Vicarage, Harcourt
St. Anthony, lying in the long grass, was living through circumstances in which the
incantation of his address was powerless to help
him.

Like Simon,
Percival senses the evil of man, the inherent evil that causes him also to be
inarticulate and powerless.  His experience parallels that of Simon, rendering him
inarticulate and well; this experience presages the one of the final scene of the novel
in which Percival

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sought in his head for an incantation that had
faded clean away.

 Young
Percival has become the subject of the Lord of the Flies, powerless to dispel the evil
and savagery that dominates the island.  When the sea captain arrives, it appears to be
too late for Percival's
rescue.