n 1880 Bois-Reymond made a famous speech before the Berlin Academy of Sciences outlining seven "world riddles" some of which, he declared, neither science nor philosophy could ever explain.[2] He was especially concerned to point out the limitations of mechanical assumptions about nature in dealing with certain problems he considered "transcendent". A list of these "riddles":
the ultimate nature of matter and force,
the origin of motion,
the origin of life,
the "apparently teleological arrangements of nature," not an "absolutely transcendent riddle,"
the origin of simple sensations, "a quite transcendent" question,
the origin of intelligent thought and language, which might be known if the origin of sensations could be known, and
the question of freewill.[3]
Concerning numbers 1, 2 and 5 he proclaimed: "ignoramus et ignorabimus": "we do not know and will not know.