There will be much huffing and puffing during Judge Sotomayor's confirmation hearings about "Judicial Activism." The problem is that it is a meaningless concept. Conservatives have adopted the label to mean any so-called liberal decision. They contrast "true" judging with "activist" judges who ignore the "true" meaning of the Constitution and simply impose will on the country.
The real question is deference to the political branches. How much leeway will a judge give the democratically elected branches? Will Judges second guess them or will they give them wide berth to make decisions, even if those decisions are bad ones? Is it activism to overturn Congressional statutes because the Court did not think Congress made a good enough case for the law? And where is the line between deference and abdication? During the Separate but Equal era was the court simply deferring to the political branches or abdicating their role to enforce the Equal Protection clause?
Deference, especially to Congress, has been the standard for most of our history. New Deal liberals leveled the activism charge against conservative supereme court justices who blocked hundreds of progressive state and federal laws. The Roosevelt appointees deferred to Congress but became increasingly vigilant about Individual rights issues. The Warren Court completed this transition giving Congress (and the states) virtually free reign in economic & social matters but closely monitoring their infringements on individual rights. Old time New Dealers and conservatives joined cause in attacking the court for its Judicial Activism. Since then, the definition has hardened along ideological lines. Conservatives see activism in individual rights cases - like Roe v. Wade - while liberals see activism in the new federalism cases - like Lopez and Morrison.