 During the period of the Roman Empire and the Middle Ages, philosophers elaborated on the existing conception of anger, many of whom did not make major contributions to the concept.For example, many medieval philosophers such as Ibn Sina (Avicenna), Roger Bacon and Thomas Aquinas agreed with ancient philosophers that animals cannot become angry.On the other hand, al-Ghazali (Algazel), who often disagreed with Aristotle and Ibn Sina on many issues, argued that animals do possess anger as one of the three "powers" in their heart, the other two being appetite and impulse.