The final and open pretext for war was the exclusion of Megara from all Athenian markets; this step meant the extinction of the town as a trading-centre and was a definite set-back to the economic development of the Peloponnese, of which Corinth and Megara were the natural avenues to northern Greece. The cup was full; Athenian ambition had run its course. The aggrieved states of the Peloponnese were invited to put their case at Sparta; Corinth drew a famous picture of the Athenian character, its restlessness, energy, adaptability and inventiveness. "In the face of such a rival," they added, "Sparta hesitates; in comparison Spartan methods are antiquated, but modern principles cannot help prevailing; in a stagnant state conservative institutions are the best, but when men are faced with various difficulties great ingenuity is essential; for that reason Athens through her wide experience has made more innovations." An Athenian reply failed to convince the allies of her innocence; one of the Spartan Ephors forced the congress to declare that Athens had violated the peace. A second assembly was summoned, at which the Corinthians in an estimate of the Athenian power gave reasons for believing it would eventually be reduced. They further appealed to what has never yet failed to decide in favour of war--race antagonism; the Athenians and her subjects were Ionians, whereas the Peloponnesians were mainly Dorians. The necessary vote for opening hostilities was secured; but first an ultimatum was presented. If Athens desired peace she must rescind the exclusion acts aimed at Megara. At the debate in the Athenian assembly Pericles, the virtual ruler, gave his reason for believing Athens would win; he urged a demand for the withdrawal of Spartan Alien Acts aimed at Athens and her allies and offered arbitration on the alleged grievances. It is well to repeat the causes of this war: trade rivalry, naval competition, race animosity and desire for predominance. Till these are removed it is useless to expect permanent peace in spite of Leagues or Tribunals or Arbitration Courts. Further, it should be noted that Thucydides takes the utmost care to point out the excellent reasons the most enlightened statesmen had for arriving at contradictory conclusions; the event proved them all wrong without exception. The future had in store at least two events which no human foresight could discover, and these proved the deciding factors in the conflict.