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.
Christian von Ehrenfels
Christian von Ehrenfels (also "Maria Christian Julius Leopold Freiherr von Ehrenfels"; 20 June 1859 – 8 September 1932) was an Austrian philosopher, and is known as one of the founders and precursors of Gestalt psychology.