 All of this detailed biological discussion helps explain the emergence of the perceptive faculties in animals and human beings. Both have sensation so that they can receive the impressions produced by external objects and, through the imaginative faculty, they can retain sensibles while no longer being in contact with the exterior world. Animals are able to react to the external world because they possess sensation and imagination, so they can experience pleasure and pain, or detect those situations that are damaging or dangerous for them. In the case of human beings, in addition to the imaginative faculty, the rational faculty is essential for cognition: human cognition is characterized not by the mere attainment of sensible forms but, rather, by the attainment of intelligibles. Furthermore, it is the faculty through which human beings attain the sciences and the arts, and through which they are able to discern between good habits and good deeds from those that are bad. By this faculty humans are able to reflect on whether something should be done and they can recognize what is useful, pleasant, and harmful (al-Fārābī VC: 165).