In philosophy his main efforts have been his opposition to positivism and his attempt at a new metaphysical theory. His independent position was arrived at after successive periods in which he followed Hegel, Schopenhauer, and Hartmann.
Volkelt spent time analysing the meaning of dreams, and captured his analysis in Die Traumphantasie. He is cited several times in The Interpretation of Dreams as a foundation for Sigmund Freud's claims.
Volkelt believed that elements of a dream were directly related to the body of the dreamer, such as a dreamed roaring stove representing the dreamer's lungs.
Volkelt has written on aesthetics as well as on philosophy proper. His more important works are:
- Pantheismus und Individualismus im System Spinozas (1872)
- Die Traumphantasie (1875)
- Kants Erkenntnistheorie, a searching piece of criticism (1879)
- Erfahrung und Denken. Kritische Grundlegung der Erkenntnistheorie became a standard textbook on epistemology, especially due to its thorough examination of the concept of 'experience'. (Hamburg and Leipzig, 1886)  Reprinted with introduction and Index by Harald Schwaetzer 2000.
- Aesthetische Zeitfragen (1895)
- Arthur Schopenhauer, seine Persönlichkeit, seine Lehre, sein Glaube (1900)
- Die Kunst des Individualisierens in den Dichtungen Jean Pauls (1902)
- Phänomenologie und Metaphysik der Zeit (1925)
- This article incorporates text from a publication now in the public domain: Gilman, D. C.; Peck, H. T.; Colby, F. M., eds. (1905). "Volkelt, Johannes Immanuel". New International Encyclopedia (1st ed.). New York: Dodd, Mead.
- Freud, Sigmund. The Interpretation of Dreams. Barnes & Noble Books, New York. 2005. Page 80.