'The Evidence Act focuses upon fact and all other things are incidental to it.' Explain it

The entire evidence act is based upon the requirement of proof and disproof of fact i.e. the entire set of proceedings related to the evidence act is aimed at either proving or disproving the facts in issue and relevant facts.  The burden of proof, the presumption, the oral and documentary evidence, the examination of witnesses etc. all are related to the  proof or disproof of facts in issue and relevant facts.

The term 'fact' has been defined in section 3 of the Indian Evidence Act 1872, to be a thing, state of thing, relation of things which can be perceived through the senses that is something which is tangible and perceptible through the sense organs. These facts are physical facts as they are physically perceptible at the same time the facts also includes the mental facts or the psychological facts that is the facts which are in the form of state of mind of a person for example intention, knowledge, good faith, reason to believe etc. and the concerned person is conscious of the said state of mind.

Section 3 emphasis upon the conciousness of the mental facts and thus excludes from the domain of facts. Those mental facts which is within the sub -consciousness of the person which is not aware of that. The definition of fact is not exhaustive though it categories physical mental are exhaustive and hence Section 3 uses the words ' means and encludes' .
Fact has been classified for the purpose of evidence act as the principal and the evidentiary fact. The principal fact in suit or proceeding will be the facts in issue and the evidentiary will be the relevant fact. [The former classification has been given by Bentham while later classification has been given by Muneer.]
Both these kinds of facts can be physical as well as mental fact.
Facts in issue is the main facts or fact upon which determination of suit / proceeding would depend. Any suit or proceeding will based upon the violation of some legal rights by a person that legal right is to be found in substantive law civil or criminal. The plaintiff or prosecution will succeed in establishing the liability and also in asserting his right only if he is able to prove the elements of substantive law, which constitute his rights and its violation and he will be able to establish the extent and the nature of liability by proving those elements of substantive law which go and determine the extent of such liability. All these facts as aforesaid are those principal fact, which will get the suit or proceeding decided. These facts are what have been defined to be facts in issue in section 3 of Indian Evidence Act 1872 has been defined as follows -
"Fact means and includes -
1. any thing, state of thing, or relation of things capable of being perceived by the senses;
2. any mental condition of which any person is concious."
Thus it can be inferred that facts in issue as per the definition of Indian Evidence Act is nothing else but various elements of substantive law civil or criminal.

Since the Evidence Act defines facts in issue and CPC does not use the term facts in issue rather it is the term issue of facts; it was pertinent in order to bring assemble between the CPC and evidence. With respect to the term facts in issue it was declared that they are one and the same thing. However a issue of fact settled by the court of civil proceeding under Order XIV of the civil procedure code is a question framed by the court. A question itself can not be a fact as such and hence in the explanation to definition of fact in issue. It is not declared that these two are synonymous and it is declared in the explanation that a any fact which is to be asserted or denied in reply to the issue of fact will be a facts in issue.