Despite a renewed interest in the philosophical prehistory of logical empiricism, several texts by prominent figures such as, e.g., Moritz Schlick and Hans Reichenbach, published in non-standard journals, have escaped the notice of scholars. Here, a hitherto virtually unknown but significant review of Moritz Schlick's influential book Allgemeine Erkenntnislehre [1st ed. 1918] written by Hans Reichenbach in 1919/20 is reprinted together with comments about its background and the later development, relying on and citing from the unpublished correspondence between Schlick and Reichenbach in 1920. Since they later became the leading figures in the so called Vienna and Berlin circles respectively, this episode marks an important stage in the gradual emancipation of "scientific philosophy" from its (neo)Kantian roots.