The following Answers from our Contributors provide a range of opinions, ranging from: They are not Muslims - but this is not so important as long as they have faith; through to yes - he or she must become a Muslim.
Answers from our ContributorsNarrated Anas:
I was informed that the Prophet had said to Mu'adh, "Whosoever will meet Allah without associating anything in worship with Him will go to Paradise." Mu'adh asked the Prophet, "Should I not inform the people of this good news?" The Prophet replied, "No, I am afraid, lest they should depend upon it (absolutely)."
Volume 2, Book 23, Number 329:
Narrated Abu Dhar:
Allah's Apostle said, "Someone came to me from my Lord and gave me the news (or good tidings) that if any of my followers dies worshipping none (in any way) along with Allah, he will enter Paradise." I asked, "Even if he committed illegal sexual intercourse (adultery) and theft?" He replied, "Even if he committed illegal sexual intercourse (adultery) and theft."
Volume 1, Book 2, Number 21:
Narrated Abu Said Al-Khudri:
The Prophet said, "When the people of Paradise will enter Paradise and the people of Hell will go to Hell, Allah will order those who have had faith equal to the weight of a grain of Mustard Seed to be taken out from Hell. So they will be taken out but (by then) they will be blackened (charred). Then they will be put in the river of Haya' (rain) or Hayat (life) (the Narrator is in doubt as to which is the right term), and they will revive like a grain that grows near the bank of a flood channel. Don't you see that it comes out yellow and twisted"
Adding to the above answer:
To be Muslim you should do the Islamic 5 pillars:
Anyone can attempt to follow Jewish tradition, but to truly practice Judaism, a person must be accepted as part of a Jewish community, and that involves conversion. Someone from a Hindu background who is accepted as a convert is no longer a Hindu, just as someone from a Christian background who is accepted as a convert is no longer a Christian. Once a conversion is complete, the convert is a Jew, who, it is hoped, will practice Judaism.
When someone thinks that means they have there own opinion. When someone believes something that means they think it is right.
Someone who believes in all gods is called a polytheist.
An internationalist is someone who believes that all nations should cooperate with each other. Also, nations should have an understanding, and practice equality amongst each other.
The definition of a nudist is someone who believes in the practice going nude. Many prefer that this is done in private, secluded area, but others are comfortable with being in the open with others.
Nonconformist? Someone who does not conform to the ideas (or norms) of society.
A theist
Religious.
A creationist.
Someone who truly believes in angels
Someone who believes the doctrine of free will
If they are not good at it because they don't understand it then practice will make limited difference. But if (or when) they do understand it, practice should help reduce silly mistakes.