Einstein preferred his violin to science. Mozart would rather have been a dancer than a composer. One wonders what the five members of the Supreme Court majority would rather be doing. Clearly their hearts, not to mention their minds, are not in constitutional law.

Last week, the court, now the second legislative branch of the federal government, continued its campaign to purify American democracy, this time by ridding it of a blemish (as the court sees it) traditional to democracy. The tradition is patronage. It is a practice as old as this republic, one favored by the Founders but, we now learn, incompatible with the Constitution they wrote and ratified.

In 1980, Gov. Jim Thompson of Illinois, a Republican, instituted a hiring freeze under which state officials were forbidden to hire, fill vacancies or create new positions without the governor's permission. Various aggrieved people sued, claiming that under the freeze the governor was running a patronage system. When granting exceptions to the freeze, the governor's agency emphasized party registration support.

Justice Brennan, joined by White, Marshall, Blackmun and Stevens, argues that the court is only making a minor extension to 1976 and 1980 rulings. Those rulings said that conditioning public employment on political affiliation unconstitutionally inhibits the exercise of fundamental rights in a way ''tantamount to coercion.''

Justice Scalia, dissenting, says: ''The public official offered a bribe is not 'coerced' to violate the law, and the private citizen offered a patronage job is not 'coerced' to work for the party.'' Furthermore, Scalia, joined by Rehnquist, O'Connor and Kennedy, argues that patronage can conduce to good government.

Scalia cites various arguments that patronage serves the public good. They include:

Patronage strengthens party discipline and combats political fragmentation, thereby protecting elected government from small, cohesive interest groups.

Patronage thickens the ranks of party activists and allows them to rely more on people-intensive and less on money-intensive campaigning. By concentrating party cadres on practical rewards, patronage discourages ideological excesses and encourages moderate two-party systems. Patronage has often been a means for the political inclusion of previously excluded minorities.

Scalia stresses that the court need not find these arguments persuasive; neither need it ignore the undeniable drawbacks of patronage systems such as incompetence and corruption. The court should only see that balancing the good and bad facets of patronage systems is a political judgment best left to political institutions. Scalia's contention is only that the court should acknowledge that a patronage system can be a reasonable political choice that the people's elected representatives are permitted to make.

Some disbursement of jobs on the basis of political affiliation must be constitutional. Otherwise, every president's Cabinet would be unconstitutional. How deeply the patronage knife should cut is a question about which reasonable communities can differ. And not all answers will be reasonable. But ''unreasonable'' and ''unconstitutional'' are not interchangeable adjectives.

The court, intoxicated by its institutional arrogance and ideological abstractions, offers no deference toward the wisdom of American communities, expressed through the democratic process, as they adopt various mixes of patronage and merit systems. The court is unprincipled -- it must be -- when it asserts a constitutionally correct line between these two components of any government hiring system. No constitutional principle regarding the correct mix of patronage and merit systems can be wrung from the document.

Once the court rejects the constitutional relevance of America's political tradition, and once it also acknowledges, as it must, that some politically based employment is permissible, then the court, says Scalia, ''has left the realm of law and entered the domain of political science.'' But because politics is not a science, the court must legislate its preferences.

The court is both doctrinaire and imprecise. The court says patronage is impermissible except when party affiliation is an ''appropriate requirement.'' Meaning what? Nobody knows. The court will legislate on that in future cases.

Lower courts, struggling to implement the Supreme Court's previously expressed preferences, have held that it is constitutional to discharge on political grounds a regional director of a rural housing administration, but not a director of roads; the second-in-command of a water department, but not the vice president of a development bank. Such incoherence is the result of the Supreme Court's capriciousness, which is unconstrained by constitutional principles.

The Supreme Court is subverting actual democracy in the name of its ideal of democracy.