Those are propositions of inner sense...

Those are propositions of inner sense, which on the one hand we find by presence concomitant with cognition, for example, the very state of fear, and on the other hand, we perceive the mental form related to it directly. Therefore, the propositions, “I am”, or “I am afraid”, or “I doubt”, are completely indubitable. So, these propositions (propositions of inner sense) are the first propositions whose value is one hundred percent proven, and there is no way for them to be in error.

To be sure, we must take care that these propositions are not mixed with mental interpretations, as was mentioned in lesson thirteen. We find such an overview in the propositions of logic, which describe other mental forms and concepts.…