N.K. Chauhan 
The data of historical sources is subject to two types of evaluation. These two types are:
1) External evaluation (external criticism)
The technique of testing the degree of authenticity of document is called External Criticism or "Heuristics" or "Lower Criticism".The "External Criticism" is of a less intellectual type of criticism of the documents.
It includes examinations of document like manuscripts, books, pamphlets, maps, inscriptions and monuments (स्मारक).
The problem of authenticity of document arises more in case of "manuscripts (हस्तलिपि)" than the printed documents because the printed document have already been authenticated by the editor.
Historian has to resort to a number of tests to determine the authenticity of a particular document in his proposed area of research such as:
1.1) Authorship
Authorship the first question while examining the authenticity of a document is its author.Even the anonymous writings can provide us useful and important knowledge.
But the discovery of an author's or writer's name adds the authenticity of the information because of the character, connections and trustworthiness of author determines the authenticity.
1.2) Date of Document
The "Date of Document", i.e. the time, place of publication of the document must be inquired to determine the authenticity of the document.In the modern publications year and place of publication is indicated on the book or document on the title page or back side (over leaf).
However in old manuscript where the data and place are absent it can be found out from the language or from the date of birth and death of author.
1.3) Textual errors
The historian confronts with the textual errors which may be either unintentional or deliberately committed.Unintentional error can take place in the copies of the documents (originals are not available).
These mistakes may be caused by the scribe, typist or printer.
1.4) Terms used in document
The meaning of words often changes from generation to generation.Therefore historian must find out the meaning and sense in which it has been used in document.
The misinterpretation of terms may lead to misunderstanding of the historical development.
2) Internal evaluation (internal criticism)
The Technique of testing the reliability of the contents of document is called Internal Criticism or "Hermeneutics" or Higher Criticism.While collecting the material, it must be remembered that a document contains the idea of the man who wrote.
A historian must try to avoid the reading into meaning which author did not mean to convey and should make a sincere effort to find out the facts, even if they are contrary to his set notions and theories.
He must be able to understand the literal and real meaning of the document which is termed as "Positive Criticism".
Historian sometimes comes across documents which contradict each other, hence the need of eliminating statements and facts which are obviously wrong and false arises.
Historians have come to hold the view that all that cannot be proved must be temporarily regarded as doubtful because of the incompetency and unreliability of the author which prevents him from telling the truth even when he knows.
To assess the correctness of the fact, historian must ascertain whether author had opportunity to know the facts as an eyewitness or not.
What was his source of information and how much time elapsed between the event and the record.
It may be noted that there is a possibility that a skilful liar may deliberately create the condition, i.e. ability and willing to tell the truth with accuracy to establish the credibility of his statements.
Therefore, in those cases the credibility must not be accepted without proper investigation.
Moreover, if there is agreement between documents, we cannot draw the conclusion that the facts are definitive but we must ensure that the facts are harmonious and prove each other are interconnected.
Facts and their Synthesis
This refers to synthesizing, or putting the material collected into a narrative account of the topic selected.Synthesis refers to selecting, organizing, and analyzing the materials collected into topical themes and central ideas or concepts.
These themes are then pulled together to form a contiguous and meaningful whole.
Be sure to watch out for these four problems that might be encountered when you attempt to synthesize the material collected and prepare the narrative account.
1) Trying to infer causation from correlated events is the first problem. Just because two events occurred together does not necessarily mean that one event was the cause of the other.
2) A second problem is defining and interpreting key words so as to avoid ambiguity and to insure that they have the correct connotation.
3) A third problem is differentiating between evidence indicating how people should behave and how they in fact did behave.
4) A fourth problem is maintaining a distinction between intent and consequences. In other words, educational historians must make sure that the consequences that were observed from some activity or policy were the intended consequences.
