2. We call two melodies like melodies when they present the same succession of pitch-ratios; the absolute pitch (or key) may be as different as can be. We can so select the melodies that not even two partial tones of the notes in each are common. Yet we recognise the melodies as alike. And, what is more, we notice the form of the melody more readily and recognise it again more easily than the key (the absolute pitch) in which it was played. 3. We recognise in two different melodies the same rhythm no matter how different the melodies may be otherwise. We know and recognise the rhythm more easily even than the absolute duration (the tempo). These examples will suffice. In all these and in all similar cases the recognition and likeness cannot depend upon the qualities of the percepts, for these are different. On the other hand recognition, conformably to the principles of psychology, is possible only with percepts which are the same in quality. Consequently there is no other escape than to imagine the qualitatively unlike percepts of the two series as necessarily connected with other percepts which are qualitatively alike. Since in differently colored figures of like form, like muscular feelings are necessarily induced if the figures are recognised as alike, so there must necessarily lie at the basis of all forms also, and we might even say at the basis of all abstractions, percepts of a peculiar quality. And this holds true for space and form as well as for time, rhythm, pitch, the form of melodies, intensity, etc. But whence is psychology to derive all these qualities? Have no fear, they will all be found, as were the sensations of muscles for the theory of space. The organism is at present still rich enough to meet all the requirements of psychology in this direction, and it is even time to give serious ear to the question of "corporeal resonance" which psychology so loves to dwell on. Different psychical qualities appear to bear a very intimate mutual relation to one another. Special research on the subject, as well also as the demonstration that this remark may be generally employed in physics, will follow later.[150] FOOTNOTES: [Footnote 147: This article, designed to illustrate historically that on Symmetry, at page 89, first appeared in Fichte's _Zeitschrift für Philosophie_, for 1865.] [Footnote 148: Comp. Cornelius, _Ueber das Sehen_; Wundt, _Theorie der Sinneswahrnehmung_.] [Footnote 149: Comp. Mach, _Ueber das Sehen von Lagen and Winkeln_. _Sitzungsb. der Wiener Akademie_, 1861.] [Footnote 150: Comp. Mach, _Zur Theorie des Gehörorgans_. _Sitsungsber, der Wiener Akad._, 1863.--_Ueber einige Erscheinungen der physiolog. Akustik._ _Ibid._, 1864.] INDEX. Absolute, temperature, 162; time, 204; forecasts, have no signification in science, 206. Abstract, meaning of the term, 240. Abstraction, 180, 200, 208, 231.