The validation of regulatory test methods - Conceptual, ethical, and philosophical foundations.

Validation establishes the reproducibility and relevance of regulatory test methods, particularly for new approach methods (NAMs) as alternatives to animal testing. While validation concepts provide a framework to assess method suitability, they rarely undergo method-critical assessment. This paper explores the philosophical and ethical foundations of the validation process, drawing from various philosophical traditions and contemporary ethical frameworks. How validation intersects with utilitarian principles, ethics of responsibility, and post-modern critiques is examined, offering a multifaceted perspective on its role in scientific progress and societal values. The paper argues for a paradigm shift in validation, moving beyond traditional animal-based comparisons towards more flexible, fit-for-purpose approaches that embrace emerging technologies and ethical con-siderations. Key ethical principles guiding NAM validation are discussed, including beneficence, non-maleficence, justice, and respect for animal welfare. Integrating these principles with scientific rigor can create a more holistic validation framework that balances human safety, animal welfare, and technological innovation. By critically examining the philosophical underpinnings of validation, this paper aims to stimulate dialogue on reforming the process to better align with contemporary scientific knowledge, ethical standards, and societal expectations. It calls for a more adaptive, transparent, and ethically grounded approach to validation that can accelerate the adoption of innovative and human-relevant toxicological methods while maintaining scientific integrity and public trust.