Empiricism is the philosophy that holds that sense experience is the derivation of all human understanding, and that you can never guarantee the existence of anything beyond your senses. Empiricists believe that all human learning takes place as a process of sensory stimulation, such as a student listening to a teacher, reading the words on the pages of textbooks or learning from the pain of making mistakes. For instance, a person locked in a single room until he was 30 would leave the room with no knowledge of the outside world, the way it works or how to function within it.
Hermeneutics is the philosophy defined by Hans-Georg Gadamer that states that you can never fully understand history or the things you read. Instead, you go through a process of interpretation, in which you learn more about the world at the time of writing, and the writing itself reaches to you, wanting you to interpret it. The result is a process of interpretation in which you can gain information and perspective about a written work, even if you can never fully understand the work. For Gadamer, the limit of learning is the point at which you surrender to a work and accept the interpretation you developed.
Renee Descarte and John Locke questioned the nature of the sense experience. John Locke questioned whether color exists, or if it is just a result of your mind's interpretation of color. Descarte questioned whether you could trust any of your senses as they pertain to things outside of your body. For Descarte, the limit of human learning was internal, because any external information had to be questioned for validity. For instance, if you reach out and touch a friend's arm, you can feel the sensation of touching; however, how can you ensure that you are actually touching that person? Other influences can manipulate your senses and trick your mind.
Plato argued that there is no limit to learning. He continued by explaining his concept of the universal human mind, Plato's philosophy about the interconnected nature of human understanding and its divine origin. For Plato, the process of learning was actually a process of remembering information from the greater universal mind. Plato believed that the universal mind connected everyone, including the divine, and it was each person's responsibility to remember the things he needs to know.