I. Philosophy:

In pre-Islamic times in Iran, philosophy was not completely separated from religion as became the case in Greece. For this reason we rarely find names of individual philosophers and philosophical schools belonging to this period. Nevertheless, the presence of philosophy, in the sense of wisdom, in ancient Iran is attested by the fact that Pythagoras claimed to have traveled to the East to study philosophy and Plotinus, the founder of the school of Neo-Platonism, joined the Roman army with the hope of going to Persia to learn about the philosophy. In any case there can be discerned in pre-Islamic times a philosophy based on light and the importance of the angelic world in the governing of this world that is closely allied to the teachings of the various Iranian religions, especially Zoroastrianism.
During this period there was also some direct contact with both Indian and Greek modes of thought. Work was translated from Sanskrit and Greek into Pahlavi and an acquaintance with Greek ideas is evident in some of the writings of the Sassanian period. Moreover, when Justinian closed the school of Athens in 529, the last philosophers of this school fled to Persia and spent some years here, where they were treated with great respect.

It was particularly during the Islamic period that philosophy flourished in Persia. From the ninth century AD when Greek philosophical texts were translated into Arabic, activity was greatly stimulated among Muslim philosophers, the great majority of whom were Persians. The first important philosophical school was the Aristotelian or Peripatetic school that included elements of the philosophy of Aristotle, the Neo-Platonist, and the teachings of Islam. The first great figure of this school, al-Kindi, was an Arab. Other important thinkers were Persians, such as ,.al-Farabi and Avicenna, with whom the school reached its peak. Most of them, however, wrote in Arabic, the sacred and scientific language of Islam, and so have come to be known in the West as Arab philosophers.
Avicenna (or Ibn-e Sina) was the greatest philosopher-scientist of Persia and also of Islam. Like most learned men of his day, he had a mastery of nearly every branch of knowledge, but it was especially in philosophy and medicine that he excelled. His work in these fields were taught for centuries in Europe.
I-yhazzali, the most famous theologian and one of the foremost religious thinkers of Islam, was a Persian, as was Abu anifah, the founder of the dominant school of Sunni law in Islam. There was also a large number of Persian Sufis of whom perhaps the most universal was Rumi.
In the twelfth century, Suhrawardi, another Persian sage, founded the philosophical school of Illumination that drew not only  on Greek sources and the tenets of Islamic revelation but also on the teachings of Zoroastrianism. It still has its adherents in modern Iran. Later, during the Safavid period, Sadr od-Din Shirazi, who is perhaps 'the greatest of Muslim philosophers, especially in the domain of metaphysics synthesized the teaching of the Peripatetic, the Illuminations, the Sufis and Shi'ism in a new school that has dominated philosophical life in Persia for the past few centuries.
The Persians have always had a taste for speculative thinking and have shown great interest in philosophy. It was therefore natural that Persia should have become a center of Islamic philosophy. This philosophy has survived to the present day as a living school and has even influenced such surrounding areas as India where Persian culture was for some time dominant.

In pre-Islamic times, scientific interest was widespread in Persia, especially during the Sassanian period. The Persians had a system of medicine of their own and also borrowed freely from the Indians and Greeks. In pharmacology they had a rich tradition that became widely known as a result of which many Persian names of drugs are to be found in other languages. Their school of thought in natural history resembled that of the Indians and was distinct from, that of the Greeks. Yet it was in Persia, in the city of Jundishapur, that the Greek tradition of medicine and pharmacology  was kept alive after the school of Alexandria and Antioch had declined. And it was in Jundishapur that the Greek and Indian medical traditions became combined with that of the Persian prepared the ground for the rise of Islamic medicine. In astronomy and mathematics pre-Islamic Persians showed much interest in calendrical calculations and also, during the Sassanian period in the compilation of astronomical records, leading to the composition of an elaborate astronomical table.
During this same period there was a continuous exchange of ideas concerning both astronomy and astrology with India and also the Near East. The Islamic period saw the translation of the treasures of ancient science into Arabic and the growth of Arabic into a universal scientific language, and Persian scientists began to flourish as never before. Indeed, during the medieval times Persia produced some of the world's greatest scientists.
In medicine the tradition of Hippocrates and Galen, along with that of the Indians and ancient Persians, was synthesized into a formidable school of medicine that reached its peak with Rhazes and A vicenna. The authority of these two masters, the second of whom was called the "Prince of Physicians" in the West, continued in European universities until as recently as two or three centuries ago. In the east also this school of medicine has survived to the present day, especially in India and Pakistan where it is practiced even more than in Persia itself. After vicenna many Persia physicians began to write in both Persian and Arabic after the example of Avicenna's medical masterpiece, the Canon. And although Islamic medicine was the product of scientists of many nations, the Persians had a large role in its formation and later development.
Other fields of science in which Persia produced important figures were mathematics and astronomy. The Persians adopted the Indian decimal system and numerals, later transmitting them to the West as "Arabic" numerals. Al- Khwarazmi, in whose book these numerals were discussed, has in fact given his name to the science of numbers called algorithm. The beginnings of algebra also were received from the Indians by Muslim and especially Persian mathematicians, and greatly developed by them. The greatest treatise on algebra during medieval times was by Khayyam, the celebrated Persian poet. Such other branches of mathematics as plane and solid trigonometry were largely developed by Muslim scientists of whom again many were Persians. In the science of numbers Ghiyath od-Din Kashani reached heights that were not matched until recently.
In astronomy the Persians made major contributions through such men as Al- Biruni, the greatest scientist of his Qay, and Nasir Od-Din al- Tusi, the director of the famous observatory of Maraghah. Muslim scholars set up new observatories, made new calculations and corrected certain of the elements in Ptolemy's astronomy. Indeed, they were the creators of the observatory as a scientific institution.