German idealism
Neo-Kantianism refers broadly to a revived type of philosophy along the lines of that laid down by Immanuel Kant in the 18th century, or more specifically by Schopenhauer's criticism of the Kantian philosophy in his work "The World as Will and Representation" (1818), as well as by other post-Kantian philosophers such as Jakob Friedrich Fries and Johann Friedrich Herbart. It has some more specific reference in later German philosophy.
Kantian ethics
Philosopher Onora O'Neill, who studied under John Rawls at ￼Harvard University, is a contemporary Kantian ethicist who supports a Kantian approach to issues of social justice. O'Neill argues that a successful Kantian account of social justice must not rely on any unwarranted idealizations or assumption. She notes that philosophers have previously charged Kant with idealizing humans as autonomous beings, without any social context or life goals, though maintains that Kant's ethics can be read without such an idealization. O'Neill prefers Kant's conception of reason as practical and available to be used by humans, rather than as principles attached to every human being. Conceiving of reason as a tool to make decisions with means that the only thing able to restrain the principles we adopt is that they could be adopted by all. If we cannot will that everyone adopts a certain principle, then we cannot give them reasons to adopt it. To use reason, and to reason with other people, we must reject those principles that cannot be universally adopted. In this way, O'Neill reached Kant's formulation of universalisability without adopting an idealistic view of human autonomy. This model of universalisability does not require that we adopt all universalisable principles, but merely prohibits us from adopting those that are not.