Hadith & the Science of Hadith

Here are the basic principles for determining the reliability of Hadith:

The Ones which could be TRUSTED:

They are MANY in numbers, and they can be trusted due to their large numbers.
They are not CONTRADICTING each other, but all are SUPPORTING each other.
They are about an event (historic event), for which there are multiple witnesses present.

The Ones which could not be TRUSTED:

The ones where Muhammad is the sole witness and no other external witness is present. For example, if Muhammad claimed that UNSEEN Jibrael came to him and the following verse or order was revealed by Allah. Such Ahadith cannot be trusted.
The ones which are SINGULAR and don't have other supporting Ahadith. It is hard to trust them.
The ones, which are many in number, but still there also exist numerous hadiths which are contradicting the first set of Ahadith.

For example:

There were originally 131 narrations that claim that Isaac was the son who was chosen for being sacrificed.

However, later, Muslim narrators fabricated 133 traditions to counter these and claim that it was not Isaac but rather Ishmael who was sacrificed.

Please read further details here:

131 Hadiths claim Isaac was the sone who was sacrificed, while 134 Traditions claim it was Ismael

Both sets of Hadith contain what are called "Sahih" (authentic) Hadith, and both reach the level of "Tawatur" (mass-transmitted). Both sets contain contradictory testimonies from the same companions, such as Umar and Ali, among others.

Logic suggests that:

It is impossible for both sets of Hadith to be correct at the same time.
Either one set of traditions is correct, or the other is.
Or perhaps, both sets are false.

Thus, this fabrication was identified based on logical inconsistencies.

Another Example: The Miracle of Moon Splitting Refuted by the Quran Itself

There are dozens of Sahih Ahadith reaching the level of "Tawatur" (mass-transmission) that claim the miracle of the moon splitting occurred in front of the Meccan pagans.

However, all these traditions are contradicted by the Quran itself.

Many verses of the Quran tell:

Muhammad used to threaten the Meccan pagans either to believe in his prophethood, or otherwise Allah would let the sky fall upon them.
The Meccan Pagans accepted this Quranic challenge and asked Muhammad to show any miracle as proof of his prophethood.

However, instead of showing a miracle, Allah (i.e., Muhammad) started providing various excuses in the Quran for why Muhammad was not able to show them any miracle. Some of these excuses are:

One Quranic verse stated that Muhammad could not show any miracle because he was only a human. However, this explanation seems insufficient, as the Meccans were not only challenging Muhammad (as a human) but also Allah to show a miracle.
Another verse claimed that no miracles could be shown because Muhammad was living among the pagans, and for his safety, Allah wouldn’t bring the skies down upon the Meccans. However, even after Muhammad left Mecca to Medina, no torment came upon the Meccan pagans, which contradicts this reasoning.
In yet another verse, Allah states that no miracle would be shown because earlier people were shown such miracles by their prophets, but they still disbelieved. However, this Quranic reasoning cannot be accepted, as the crimes of earlier people cannot logically be held against the Meccan pagans.
Similarly, in Medina, Muhammad did not show the "Miracle of Fire" to the Jewish communities there. The Quran again gives the excuse that the forefathers of the Jews killed earlier prophets, and therefore Allah would not show them miracles. Again, this is problematic, as the Jews in Muhammad’s time could not be held accountable for the actions of their forefathers

Please read all details about these Miracles here: