Are All prophets sinless?

Greetings to all;

In an email I received I encountered this question:

"you say that the Muslim faith believes the prophet must be one completely devoid of sin? Does that mean they believe the prophet Mohammed lived a life without sin? As far as I am aware, the only man who has been able to stand-up to the test of "sinlessness" is Jesus Christ . . ."

As you can see in my post on Women in Islam it is mentioned that the Shia Moslems believe that ALL prophets are sinless. According to them being sinless is very crucial criterion of being chosen as a prophet. Therefore they believe that Jesus as the messenger of the Lord is sinless as well as All other prophets including Noah, Isaac, Joseph.......Moses and of course the prophet of Islam Mohammad.

Here is a part of a book I have found concerning the reasons according to common sense behind this claim. The passage first of all talks about the logic behind prophet hood, then moves on towards why all prophets need to be unique and far above other men in terms of all their actions and then distinguishes prophets by categorizing them into "Arch-prophets" and other prophets.

Eli

NUBUWWAH (PROPHETHOOD)

While independent in every respect, the Almighty Allah, with His immense power, has created the world of existence and its various creatures, allowing them to enjoy His countless blessings.
From the first day of creation till the last day of existence, man and other creatures are fostered by Allah. They are each led toward a known and determined goal with a particular order and system. They proceed towards their ends while being exposed to His noteworthy blessings.
If we study and deliberate upon our lifetime, namely the period of infancy, childhood, youth, and old age, our conscience will testify Allah's complete favours to us. When we become more aware of this matter, our wisdom will undoubtedly judge that the Creator of the world is more compassionate to His creatures than anyone else is. Due to this compassion and favour, Allah always considers their interests and never consents to the corruption and defect of their affairs without wisdom and expediency. Mankind is one of the creatures of Allah. We know that man's interest and prosperity depend upon his being realistic and benevolent; that is to say, he must possess true beliefs, praiseworthy ethics, and good deeds.
One may say that with his Allah-granted wisdom, man can distinguish between good and bad and can recognize a well from a path.
It should be known, however, that wisdom alone cannot resolve this difficulty and lead man to realism and benevolence. All these indecent characteristics and unjust actions witnessed in the human society are committed by those who possess wisdom and discernment, however, as a result of selfishness, profit-seeking, and voluptuousness, their wisdom has been overcome by their sentiments and they have succumbed to their carnal desires, leading them astray. Therefore, the Almighty Allah must lead and invite us to prosperity through some other ways and through means which can never be overcome by carnal desires and which never make blunders or mistakes in their guidance. This path is nothing but the path of Nubuwwah.

THE LOGIC IN NUBUWWAH (prophethood)

From what. we have discussed about monotheism, it becomes evident that since Allah creates everything, its fostering also depends upon Him. In other words, the Almighty Allah is the organizer and leader of the movement of any worldly creature or phenomenon that from the very beginning of existence endeavours for its survival, strives to remove its imperfections, eliminates its needs and shortcomings one after another, makes itself independent and self-sufficient as much as possible, and moves in an orderly manner in its path of survival and existence.
A definite conclusion can be drawn from this concept. That is to say, any one of the various kinds of phenomena of the world has a specific evolutionary process for its survival which is done by its special endeavours. In other words, in the path of their survival, worldly creatures of each particular group have a series of specific functions assigned to them by Allah. As the Holy Qur'an, with reference to this fact, states:
"...Our Lord is He Who gave to everything its creation, then guided it (to its goal) (20:50)."
This order applies to all components of creation without any exception. It includes the stars, the earth, their components, compositions that generate primary phenomena, plants, and animals.
Man's condition is the same as others, in this universal guidance, but there is a difference between him and others.

THE DIFFERENCE BETWEEN MAN AND OTHER CREATURES

The earth has supposedly been created millions of years ago. It employs all its hidden forces and endeavours in the environment of its existence to the extent permitted by opposing forces. It displays the signs of its entity in the field of its rotation and transitional movement, thus maintaining its survival. Unless faced with a stronger opposing force, it will continue this activity and will not fall short of carrying out any of its functions.
For example, from the time an almond tree takes root from a seed until it becomes a fully grown tree, it assumes duties, such as nourishing, developing, etc (in other words, it performs these duties to pursue the course of its existence.) It will never refrain from carrying them out unless it is precluded by a stronger opposing force. This process also applies to any other phenomenon. But mankind performs his particular activities voluntarily and his actions originate from his thoughts and determination. Many a time, man refrains from a task which is entirely to his interests and which is not hindered by any opposing force and undertakes a task which is entirely disadvantageous to him knowingly and intentionally. Sometimes, he abstains from drinking antidote and sometimes he drinks a cup of poison and kills himself.
It is certainly clear that the divine universal guidance will not be compulsory for a creature born with free will. That is to say, the prophets conveyed the message of the Almighty Allah on good and bad and prosperity and wretchedness to the people and warned believers of Allah's chastisement, but the believers have always been free to adopt any one of them. It is true that, in general, man perceives his good and bad and advantage and disadvantage through his wisdom, but that very wisdom often loses its keenness, follows carnal desires, and makes error. Therefore, in addition to the medium of wisdom, divine guidance should positively be achieved through a different medium, which is entirely inviolable to sin and error. In other words, in addition to the medium of wisdom, the Almighty Allah confirms His orders by another medium.
This medium is the same medium of prophethood by which the Almighty Allah reveals His orders to one of His servants through wahy leading mankind to prosperity. Allah appoints him to communicate His orders to the people and to oblige them to follow the orders through hope, despair, encouragement, and threat.
The Almighty Allah states:
"Surely We have revealed to you as We revealed to Nuh (Noah), and the prophets after him...(4:163)." "(We sent) messengers as the bearers of good news and as warners, so that people should not have a plea against Allah after the (coming of) messengers...(4:165)."

ATTRIBUTES OF PROPHETS

From what was discussed, it becomes clear that the Almighty Allah, with His divine teachings, must have provided some of His servants with intuitive knowledge and laws that guarantee man's prosperity and must have sent them to lead the people.
A person who possesses divine messages is called a "nabi (prophet)" and messenger of Allah and the entire set of messages from Allah which he has brought to the people are called "religion".
It has also become clear that a prophet:
(1) Must be free and immune from error. In order to communicate what has been revealed to him to the people without error and mistake, he should be immune from forgetfulness and other mental weaknesses; otherwise, divine guidance will not attain its goal and the general guidance rule will forfeit its applicability and lose its power to influence people.
(2) Must be inviolable to error and sin both in deeds and speech, because sinfulness has no effect in propagation. People do not esteem the speech of a person whose manner and speech are at odds. They even take his deeds for his mendacity and imposture by saying if he meant what he said, he would act accordingly.
By bringing these two aspects together in one phrase, we can say that a prophet must be inviolable to errors and sins to render preaching and propagation effective. In His words, the Almighty Allah, too, refers to this point and states:
"The Knower of the unseen! so He does not reveal His secrets to any, except to him whom He chooses as a messenger. for surely He makes a guard to march before him and after him, so that He may know that they have truly delivered the messages of their Lord...(72:26-28)."
(3) Must possess moral virtues such as chastity, courage, justice, etc, for these are considered as praiseworthy qualities. Anyone who is immune to any sins and follows religion in a perfect manner will never be blemished by moral vices.

PROPHETS AMONG PEOPLE

History indicates that there were prophets among people who responded to the call of Allah; however, the details of their life is not so clear. Only the details of life of Prophet Muhammad (SA) is devoid of ambiguity. The Holy Qur'an, which is the divine book given to Prophet (SA), contains sublime religious aims, has clarified the call of the prophets in the past and has described their goals and objectives.
The Holy Qur'an stipulates that many prophets have been, assigned by Allah to lead the people, all of whom consistently invited the people to monotheism and the true religion. As Allah states:
"And We did not send before you any messenger but We revealed to him that there is no god but Me, therefore worship Me (21:25)."