Another aspect is Buddhism as Philosophy. Philosophical knowledge can be clearly seen by means of reasoned logical proofs but cannot be demonstrated experimentally. It contrasts with science, which is knowledge resulting from seeing something clearly, with our eyes, or through physical experimentation and proof, or even with the "inner eye" of intuition. Profound knowledge such as that of emptiness is just philosophy for a person who has not yet penetrated to the truth, and science for another who has done so, such as a fully enlightened individual, or arahant, who has seen it clearly, intuitively. Many aspects of Buddhism, in particular the Four Noble Truths, are scientific in so far as they can be verified by clear experimental proof using introspection. For anyone equipped with awareness and interested in studying and carrying out research, the cause - effect relationships are there just as in science. Buddhism is not just something obscure and vague, not just philosophy, as are man-made subjects.