Gustav Fechner
Fechner, along with Wilhelm Wundt and Hermann von Helmholtz, is recognized as one of the founders of modern experimental psychology. His clearest contribution was the demonstration that because the mind was susceptible to measurement and mathematical treatment, psychology had the potential to become a quantified science. Theorists such as Immanuel Kant had long stated that this was impossible, and that therefore, a science of psychology was also impossible.
Donald O. Clifton
Donald O. Clifton (February 5, 1924 – September 14, 2003) was an American psychologist, educator, author, researcher, and entrepreneur. He founded Selection Research, Inc., which later acquired Gallup Inc., where he became chairman, and developed CliftonStrengths, Gallup's online psychological assessment. Clifton was recognized with a presidential commendation from the American Psychological Association as "the father of strengths-based psychology and the grandfather of positive psychology".