1.God exists, is omnipotent, omniscient, and wholly good
2.The tsunami caused people to suffer
3.An omniscient and omnipotent good being prevents any suffering that it can properly eliminate(that is, eliminate any suffering without eliminating an outweighing good or bringing about a greater evil)that it knows about
4.An omnipotent being has the power to prevent anything
5.An omniscient being is all knowing
6.The tsunami did not bring about good
Conclusion: God should have prevented the tsunami
The premises listed above are plausible because they support the conclusion.. The tsunami caused a lot of people to suffer. It was an evil that only brought about more evils like famine, poverty, despair, and death. Assuming that God exists, is all powerful, all knowing, and really good, then he could not have allowed the tsunami to cause the destruction that it did. God, as the being described in premise 1, should have properly eliminated the tsunami since He knew about it and the damage it would do.
Premise 1,4, and 5 were used in the argument to basically establish the type of being that God is. If we are to believe that God has enough power to prevent anything and knows about everything, it is reasonable to say that God had the ability to prevent the Asian tsunami.
Alternative premises that just stated: God is all powerful and God is wholly good would not have been sufficient because God could have somehow not known about the suffering caused by the tsunami. Hence, an additional the quality of omniscience needed to be add to the premise. Also, as Plantiga states in his book, it is not necessarily true that A good being should prevent all suffering it has the power to prevent . Eliminating an evil could bring about more evil or outweighing a good. Therefore, it was necessary to add that A good being prevents evil it can properly eliminate to my premises.