Conceptual or philosophical issues are particularly controversial in contemporary special education. Basic philosophical issues are certainly not peculiar to special education, nor are the controversies about doubt, certainty, or the best bases for human dignity or social justice anything new. The usual special/general education division might be considered to involve only two "tiers". Response to intervention (RTI) and other multi-tiered systems of support (MTSS) involve more than two "tiers". The purpose of MTSS frameworks is not to classify students but to make informed decisions regarding what interventions to deliver and the resources needed to provide them. The use of evidence-based practices in the context of RTI and MTSS decision-making is not confined to special education. To the contrary, effective practices are important to ensuring the academic and behavioral success of all students. Disproportionality in special education is most often assumed to be primarily a matter of bias in evaluation and decision-making.