Cartesian Bias is our instinct to impose Cartesian geometry on our mental models of the space around us. Cartesian geometry was defined by Rene Descartes in the fifteenth century, but our subconscious bias towards it evolved long before that as a special case of story-telling bias. Modern physicists theorize that the Cartesian model of space/time is only an approximation of reality. Our bias towards it is so strong, however, that, instead of rejecting the simplification outright, physicists express more accurate models of the universe as corrections to the Cartesian view. Quantum theory and the theory of relativity are examples of such corrections.

    According to the Cartesian view, space exists independent of the objects that may or may not exist inside it. This contrasts to geometries, such as that of cyberspace, in which "space" is no more than a property of objects, a metaphor describing their relationships to each other. Since humans only measure space and time by bounding them with objects, we will never be able to empirically prove which of these kinds of space/time most accurately describes reality (nor should we care). Einstein's theory of relativity reflects these limits of our perspective by expressing space and time as functions of the objects they hold, suggesting that space and time "bend" in response to the velocity and force between the observer and observed objects.

    The Cartesian view of space and time also includes the notion that each object has its own position and trajectory, independent of other objects. Again, this is something we'll never be able to confirm, since space and time (in terms of which we measure positions and trajectories) is supposedly "bent" by surrounding objects. Thus, as far as we can tell, the positions and trajectories of objects may only exist relative to other objects. Quantum theory circumvents this issue by modeling positions and trajectories as probability distributions. By thus sacrificing the notion of singular position and trajectory, we avoid the need to account for all of the influences of surrounding objects. This permits us to preserve the notion that objects have independent positions and trajectories.

    Since we don't usually face relativistic and quantum extremes directly, it was natural for humanity to evolve an instinct for the Cartesian view. By 1781, Immanuel Kant even mistook this viewpoint to be a fundamental property of intuition. Now, unfortunately, we must struggle against it to reach a full understanding of relativity and quantum mechanics. That's why these theories are usually addressed fully only at the culmination of a scientist's education. Much as young children find it difficult to understand how short wide vessels could possibly hold as much as tall thin ones, it takes a great deal of intellectual maturity to understand how the geometry of our universe could possibly differ so much from the Cartesian geometry we've instinctively assumed all our lives.

     We should try to be aware of natural biases, but, unfortunately, we can never be sure that we're aware of them all. The only way to avoid bias completely is to avoid relying on intuition. The next chapter gives step-by-step instructions for how predictive deduction can be implemented consciously. Especially for critical cases, we should use it, instead of intuition, since the more consciously we reason, the less opportunity biases have to interfere.