I. The rationale for official intervention, 443. — II. Aliber's rebuttal of the common-sense view that intervention is unwise if the authorities themselves believe parities may be changed, 445. — III. The case of a nonreserve-currency country, 446. — IV. Losses to speculators vs. the devaluation profit, 451.—V. The special case of the dollar, 452. — VI. Summary and conclusion, 454.