Final answer:
Justice Brennan applies Holmes' idea by rejecting legal formalism, promoting judicial activism, and emphasizing precedent.
Step-by-step explanation:
Justice Brennan applies Holmes' idea in the current case by rejecting legal formalism and promoting judicial activism. He emphasizes precedent by interpreting the Constitution as a "living" document, which allows for the adaptation of its text to modern understandings of equality. This approach enables the court to make decisions that align with contemporary social needs and ensure individual rights and liberties are protected.