if he told the participants beforehand to report on the numbers observed, then they were unable to describe the letters, colors, or shapes with any accuracy after the experiment. If he told participants to describe the colors, then with subsequent questioning they were unable to describe the letters, numbers, or shapes. The item people could describe with the highest level of accuracy was always the item they were instructed to observe. These results indicated that they subjects of the experiment would abstract the requested features, while at the same time remaining “unconscious” to all of the other present features. Külpe wrote in a letter about the conclusions from these experiments: "The old doctrine of an inner sense with the involved idea of a distinction between the reality of consciousness and objectivity must now have its opportune renewal in the domain of psychology. This is the principal conclusion I would draw from my experiments. In connection there with I define abstraction as the process by which the logically or psychologically effective is separated from the logically or psychologically ineffective. The effective partial contents are positively abstracted for thinking and ideation. The ineffective are those from which the abstraction is made. For our consciousness, therefore, there are abstract ideas, for psychical reality there are only concrete ideas. At the same time the old controversy between nominalism and realism approaches its solution." In another letter, Külpe identified a key distinction in his ideas as compared to Wundt’s ideas. Külpe differentiates 'thought' from 'thinking'. Thoughts are 'contents’, he argues, whereas thinking in its various forms such as meaning, judging, and concluding can be considered acts or functions. In this case, the contents are the thoughts themselves, whereas the acts or functions are the thinking process. To Külpe, function and content are different and independently variable. He proposed that the acts or functions are not analyzable in consciousness, are relatively unstable, and can only be observed and known after an event has occurred. In order to observe them, Külpe’s process of systematic experimental introspection is critical. Külpe believed that contents, on the other hand, are analyzable in consciousness, observable in introspection, and relatively stable. He also cautioned against speculating about what is occurring physiologically at the time of thinking. Instead, Külpe encouraged the finding and improving of facts on the subject. That is, ignore the physiological processes occurring as part of the thinking process but