To Dr Mark J. Valencia's interesting and thought-provoking analysis ("Known unknowns of politics in the South China Sea"; June 27) can also be added the very significant but little-mentioned known "known" that when the nine-dash line was first published in the late 1940s, neither the Philippines, Vietnam, France nor the United States raised any objections.
Thus, the unknown "unknown" is whether the United Nations tribunal will consider the Philippines as having a possible case only on the validity of any subsequent deviations made to this late 1940s' line, and not on the form it was first published.
Another similarly little-mentioned known "known" is that Vietnam's claims are practically the same as the nine-dash line - that is, Vietnam also lays claim to 90 per cent of the South China Sea.
Arising from this is the unknown "unknown" that were the UN tribunal to rule in favour of the Philippines, would it, at the same time, rule against Vietnam's claims?
In fairness, the tribunal should.
But if the tribunal does so, and Vietnam rejects the ruling, it would also seriously impact the stability of the South China Sea.
Chang Wen Lam (Dr)