Ghosts and Phantoms (Metaphor)
Throughout The German Ideology, Marx often uses metaphors involving ghosts, phantoms, and other insubstantial, imaginary beings in order to illustrate the superstitious, irrational nature of the idealist position. The “ghosts” of ideology are placed in contrast to the “sensuous” reality of human life and activity, as well as to the solidity of the “ground” of history and material conditions.
Camera Obscura (Simile)
In order to emphasize the inversion characteristic of ideology, in which ideas appear to determine reality rather than vice-versa, Marx compares the process to that of the camera obscura, a contemporary technology, which was a precursor to photography, that projected an image in reverse through a small hole: "If in all ideology men and their circumstances appear upside-down as in a camera obscura, this phenomenon arises just as much from their historical life-process as the inversion of objects on the retina does from their physical life-process." The point of this simile is to make clear that the nature of ideology, even as it obscures the reality of the historical process, is itself still determined by history.
