While I can accept that Muhammad didn't have formal education as you say, and I can also agree with you that he didn't know how to read, I do disagree with you that he was "without education".
That's is either misleading, or gross understatement.
Yes, he was an orphan, but eventually he was brought up by his uncle, a merchant. Back then, getting into trade, is considered education, sort of like master and apprentice, whether it include reading/writing or not.
So Muhammad wasn't just a shepherd. It wasn't the only background, he had before became a prophet. Muhammad was even married to the widow, Khadijah, whose father was wealthy merchant.
I find that some RF Muslims or Baha'i tends to highlight his life as a shepherd, before becoming a prophet, but overlooking his upbringing and young adulthood as a merchant.
Let me share a rough chronology of events that most agree transpired and you can judge for yourself:
CHRONOLOGY OF ISLAM
c570 AD Birth of Muhammad. The Qur'án gives the year of the "Elephant", (105:1-5) as His birthdate.. This year refers to a military engagement in which elephants were employed in battle.
595 AD Muhammad married Khadijah Bint Khuwaylid who bore Him four sons (all of whom died in infancy), and four daughters, none of whom lived to age 30.
610 AD Muhammad receives a revelation on Mr. Hira. The Qur'án calls it the "Night of Qadr", or "night of power". (97:1-5). His wife Khadijah becomes the first to believe in Him.
610-613 AD Muhammad remains publicly silent as to the nature of His Mission.
614 AD Muhammad begins to teach His new Faith and proclaims Himself to be the Prophet of God.
615 AD Some of Muhammad's followers emigrate to Abysinnia (today called Ethiopia).
616-618 AD Boycott imposed on Muhammad and His followers by Meccans. 'Umar is converted to Islam.
619 AD Khadijah dies. Abu Talib, Muhammad's uncle and protector, also dies.
619 AD Muhammad goes south to the city of Taif to teach His Faith but is stoned and driven from the town.
620 AD Muhammad experiences the "Night Journey" ('Miraj'), a dream or vision in which He is transported to the Haram--the platform on which the Dome of the Rock stands today--in Jerusalem and from there to into heaven. Six visitors from Yathrib (today called Medina) accept Muhammad.
621 AD Muhammad sends a believer to Yathrib (Medina) to teach His new converts.
622 AD July 15th is given as the traditional date on which Muhammad 'emigrates' ('hegira') to Yathrib (Medina). 622 begins the Muslim lunar calendar as 1 A.H. (A.H.="After the Hegira").
623 AD Battle of Badr. Read (3:123). Muhammad and His followers rout a numerically superior Meccan army.
625 AD Battle of Uhud takes place on the western outskirts of Medina.. Muhammad and His followers lose to the Meccans.
626 AD January - Husayn born to 'Ali and Fatimah, Muhammad's son-in-law and daughter. Husayn is to become the Third Imam of Shi'ih Islam. M&TCOI, p.92.
627 AD "Battle of the Trench". Siege of Yathrib (Medina) by Meccans foiled by the military tactic of digging a trench around most of the city.
628-9 AD Muhammad enters in to a ten year truce with the Meccans called the Treaty of Hudaybiyyah.
630 AD Muhammad marches on Mecca with 10,000 men. Battle of Hunayn fought 31 January.
632 AD Death of the Prophet's son Ibrahim. Muhammad's last pilgrimage to Mecca. June 8th, traditional date on which Muhammad dies in 'A'isha's (3rd wife) arms.
- From a brief guide by Duane Troxel...