THE ARM CHAIR RULE
Ambit of Section 75
This section incorporates what is known as the armchair rule. This rule enables the court to admit extrinsic evidence in aid of interpretation of will. In order to give effect to the words used in the will and when meaning of these words and their application cannot be ascertained without knowing something more than this rule permits admission of, extrinsic evidence relating to the fact and circumstances respecting testator’s property and his family and other persons and things as on the date of will, although it is often said that the will speaks from the date of the death of the testator. 
Extrinsic Evidence of Surrounding Circumstances
It is very difficult to state precisely or even to list as to which are facts about the will or its surrounding circumstances of which extrinsic evidence can be given. The courts have considered many facts, such as race, religious beliefs and opinions. In order to show what things the testator intended to dispose of, all the circumstances relating to property of the testator material to identify of the thing described are admissible.  Similarly, the court may look into every material fact relating to the persons who claim to be interested under the will and to the circumstances of the testator and of his family and affairs, to identify the persons intended to be benefited by the testator. In other words, the extrinsic evidence as to the following two matters is admissible –
the state of property which is the subject matter of bequests (this is done with a view to identifying the property bequeathed)
the beneficiaries with a view to identifying the persons to whom the property has been bequeathed.
Under the present section, extrinsic evidence is admissible not as to the property acquired after the date of execution of the will but of the property he had at the date of the execution of the will. Similarly, extrinsic evidence is admissible of what the testator had written and not of what he intended to have written. If legatee is correctly described in the will, no further enquiry is needed and extrinsic evidence is not admissible to identify or dis-identify him. But where a legatee named in the will is not identifiable, evidence may be shown that the testator had used the nickname of the person whom he wanted to benefit.
In sum, when the testator has left no uncertainty as to the beneficiaries or as to the property bequeathed no extrinsic evidence can be admissible, but if there is any uncertainty as to these, extrinsic evidence is admissible.  Extraneous evidence is also admissible to prove that a will was executed through fraud or mistake. Thus evidence may be adduced to prove that clauses or expressions have been inadvertently introduced into the will contrary to the intention and instruction of the testator, or, in other words that part of the executed instrument is not his will.  Evidence is also admissible in order to ascertain how words used in a will are related to existing facts, say for example, to prove that persons and property actually exist as described in the will.  But the court must first attempt to construe the word as used in the will. 
Scope and Principle
The section embodies partly a rule of construction and partly a rule of evidence. It specifies the grounds for admission of intrinsic evidence for construction of a will. It was laid down as early as in Rebati v. Shibnandan  that in construing a written document the position of the parties must be looked into and the deed must be construed with reference to the situation of the parties and their rights at the time the document was executed.
The principle of English law on the point was clearly expounded in the case of Stringer v. Gardener,  wherein it was laid down that in every case of ambiguity whether latent or patent, oral evidence is admissible to show the state of testator’s family or property. Thus, where the words were plain and unambiguous but not at the date of will, say for example, where the person described has died, extraneous evidence may be admitted to discover some other existing fact as on that date to explain the words as understood by the testator. But extrinsic evidence is not admissible to enable the court to construe a will where the words themselves do not require any interpretation, but the difficulty is only in the construction of sentence containing such words. 
Requirements of the Testamentary Capacity
It has been observed by the courts that the primary duty of the court is to ascertain the intention of the testator from the will itself, without making any conjectures or speculation as to what the testator would have done had he been better informed or better advised,  following Venkata Narasimha v. Parthasarthy, Mukherjea J., observed: “All authorities agree that in a will the cardinal rule to be observed is to ascertain the real intention of the testator which the will itself by express words or by implication declares and the primary duty of the court is to ascertain from the language of the entire document what the intentions of the testator are. The court must consider the surrounding circumstances, the position of the testator, his family relationship, the probability that he would use words in particular sense and many other things which are often summed up in the somewhat picturesque figure, “the court is entitled to put itself in the testator’s armchair".
The Privy Council observed that the court must place itself in the arm-chair of the testator and take into consideration the surrounding circumstances, the status of the testator, his family relationship and many other things, in construing a will, for testator is in an environment with reference to which he acts.  The intention of the testator has to be gathered primarily from the language of the document which is to be read as a whole. The court is entitled to put itself into the testator’s armchair. But all this is solely as an aid to arriving at a right construction of the will. The duty of the courts is to carry out the intention as expressed and none other.  In determining the real intention of the testator the entire document has to be construed as a whole. No word, phrase or clause should be ignored. After reading the will as a whole, the court should arrive at the intention of the testator and if there are any ambiguous or mutually contradictor clauses appearing in the will, they should be interpreted and given meaning in accordance with the intention of the testator. For that purpose, effect should be given to every disposition contained in the will.  The surrounding circumstances that the court may look into are the race and religion of the testator, and opinions then prevailing. But these are merely aids at arriving at the real intention of the testator. The court has no power to give effect to a hypothetical intention of the testator by supplying so called lacunae in the will and thereby making a new will for the testator. The court should not speculate as what testator might have intended to write in the will. The court has to interpret the will from the testator’s point of view and not to make a new one in conformity with its own notions of law, that the testator’s property is to be equitable distributed. 
The court should carry out the intention of the testator as expressed in the will or impliedly inferred from it.  In short, the court cannot make a will for the testator. It can only construe the will as made by the testator. Furthermore, in construing a will, the true intention of the testator has to be gathered not only by attaching importance to isolated expressions here and there, but by reading the will as a whole without discarding any provisions as redundant and contradictory.  It was observed in the case of Suna Ana v. S.R. Ramaswami  the Privy Council said that where a will has been made and is apparently in perfect form, the evidence of attesting witnesses is to be appreciated and trusted. Few things can be more dangerous that to attempt to recreate the will on the supposed assumption what in the opinion of the court the testator might have written in the will. The court can only supply the missing words to carry out the intention of the testator. But where the intention is clear, the court is not justified in supplying supposed missing words in the will.  Intention must be expressed in expounding a will and the court must ascertain not what the testator meant, but what is the meaning of the words he used. 
Furthermore, in an old decision of the Privy Council it was observed: “In construing a will the primary duty of a court is to ascertain from the language of the testator what were his intentions and in doing so they are entitled and bound to bear in mind other matters than merely the words used. It is justified in refusing to allow defects in expression in these matters to prevent the carrying out of the testator’s true intentions. These intentions must be ascertained by the proper construction of the words he uses and once ascertained they must not be departed from". 
In the case of Navneet Lal v. Gokul,  certain rules as to interpret a will were provided by the court which were established taking into consideration the earlier decisions of the courts and which are applied by the courts even today -
 In construing a document whether in English or in vernacular the fundamental rule is to ascertain the intention from the words used; the surrounding circumstances are to be considered; but that is only for the purpose of finding out the intended meaning of the words which have actually been employed. 
 In construing the language of the will the court is entitled to put itself into the testator’s armchair  and is bound to bear in mind also other matters than merely the words used. It must consider the surrounding circumstances, the position of the testator, his family relationship, the probability that he would use words in a particular sense... But all this is solely as an aid to arriving at a right construction of the will, and to ascertain the meaning of its language when used by that particular testator in that document. 
 The true intention of the testator has to be gathered not by attaching importance to isolated expressions but by reading the will as a whole with all its provisions and ignoring none of them as redundant or contradictory. 
 The court must accept, if possible, such construction as would give to every expression some effect rather than that which would render any of the expressions inoperative. The court will look at the circumstances under which the testator makes his will, such as the state of his property, of his family and the like. Where apparently conflicting dispositions can be reconciled by giving full effect to every word used in a document, such a construction should be accepted instead of a construction which would have the effect of cutting down the clear meaning of the words used by the testator. Further, where one of the two reasonable constructions would lead to intestacy, that should be discarded in favour of a construction which does not create any such hiatus. 
 It is one of the cardinal principles of construction of wills that to the extent that it is legally possible effect should be given to every disposition contained in the will unless the law prevents effect being given to it. Of course, if there are two repugnant provisions conferring successive interests, if the first interest created is valid the subsequent interest cannot take effect but a Court of construction will proceed to the farthest extent to avoid repugnancy, so that effect could be given as far as possible to every testamentary intention contained in the will. 
This aspect of the matter has recently been considered in Bajrang Factory Ltd. v. University of Calcutta,  wherein it was held:
With a view to ascertain the intention of the maker of the will, not only the terms thereof are required to be taken into consideration but also all circumstances attending thereto. The will as a whole must, thus, be considered for the said purpose and not merely the particular part thereof. As the will if read in its entirety, can be given effect to, it is imperative that nothing should be read therein to invalidate the same.
Specific Areas where the Arm-Chair Rule is Applied
In adjudging the existence of testamentary capacity, the factor of unnatural disposition has had dominating influence – a predominance which is only marginally lessened by the adoption of the arm-chair rule to assess the fairness of a testamentary disposition. This rule requires that, as far as possible, the court should place itself in the armchair of the testator at the time she executed the will. It should find out how the testator regarded her affairs and her disposition towards the persons she was benefiting or disinheriting. The court should ascertain whether the testator understood the nature of the act and its consequences. It should also find out if any disorder of the mind has poisoned the affections of the testator, or perverted her sense of right and wrong, or perverted the exercise of her natural faculties.  If subsequent to such an examination, the mental faculties of the testator are found functional, then capacity cannot be rendered questionable by the inequity of the disposition. Along with this ruling, courts declare that the justice or injustice of the disposition might cast some light on the question of capacity. However, if even after sitting in the armchair of the testator, the exclusion cannot be understood by the court, the testamentary capacity of the testator would stand negated. In a number of cases where wills have been invalidated, the unnatural nature of the disposition has significantly influenced the decision. Courts have found disposition to strangers more unnatural than a preference between legal heirs. Exclusion of a close relative has been found to negate the capacity only if the antipathy of the testator is so extravagant and so manifestly baseless as to amount to an affectation of the mind or a delusion. In such a state of mind, testamentary capacity has been held questionable because the testator is prevented due to the state of her mind from recognizing the natural objects of her bounty.
Thus, in Suradhani Debya Choudharani v. Raja Jagat Kishore Acharya,  the testator made a will whereby he bequeathed his property in favour of a distant collateral whilst excluding his mother and younger brother. The mother challenged the will on the ground that her son had an irrational delusion that the property actually belonged to the collaterals and had been wrongfully usurped by his branch of the family. These deluded feelings also extended towards her. Further, he had a strong aversion for her which could not be factually explained.
The court found that the mother and son had continuously wrangled over the management of the testator’s property. The mother had even initiated inquisition proceedings against the testator and his brother. Further, there were strong rumours that the mother had been unfaithful to her husband and the testator had found her in a compromising position. This had generated in him a strong dislike towards his mother. It was held that the exclusion of the mother was not based on delusion because that feeling of aversion towards her had a basis in facts. The brother was not made a beneficiary because he would not get married and the property was given to the collateral so that it would remain within the family. Also, with a codicil, the testator had made provision for the maintenance of his mother. In these circumstances, the contention of lack of testamentary capacity was rejected. Similarly, in Rajeshwari Rani v. Nirja Guleri,  it was established that the husband and wife had very acrimonious relations as a result of which the husband had excluded the wife. The contention of the wife that the husband was a schizophrenic who had made the will in a state of mental disorder was not upheld.
In Kamla Devi v. Kishorilal, the issue concerned determining which of the two wills executed by the testator was valid. The earlier will excluded the wife but made provision for the daughters. The wife was excluded because the testator doubted her fidelity. The later will excluded both the wife and the daughters. The second will was executed by the testator after a long illness and near the time of death. The second will was held invalid. The exclusion of the minor daughters was held to be unnatural and showing mental capacity. The first will which excluded the wife was, however, found valid. It was held that even if the suspicions against the wife were the result of an extremely jealous disposition, it did not negate testamentary capacity.
In the case of Bajrang Factory Ltd. v. University of Calcutta,  wherein it was held that the intention of the maker of the will, not only the terms thereof are required to be taken into consideration but also all circumstances attending thereto. The will as a whole must, thus, be considered for the said purpose and not merely the particular part thereof. As the will if read in its entirety, can be given effect to, it is imperative that nothing should be read therein to invalidate the same. In the case of Anil Kak v. Kumari Sharda Raje,  this Court stated that the testator’s intention is collected from a consideration of the whole Will and not from a part of it. If two parts of the same Will are wholly irreconcilable, the court of law would not be in a position to come to a finding that the Will dated 4.11.1992 could be given effect to irrespective of the appendices. In construing a Will, no doubt all possible contingencies are required to be taken into consideration. Even if a part is invalid, the entire document need not be invalidated, only if it forms a severable part. Furthermore, in the recent case of Shyamal Kanti Guha v. Meena Bose,  it was held that the Will should be construed by a Court indisputably placing itself on the arm- chair of the testator. The endeavour of the Court should be to give effect to his intention. The intention of the testator can be culled out not only upon reading the Will in its entirety, but also the background facts and circumstances of the case. Therefore, looking at the cases above one can observe that the arm-chair rule is still being applied by the courts to interpret a will so as to look at the intention of the testator. This rule is very much acceptable by the courts and one is able to derive the intention and the purpose of the maker of the will easily which not only helps the court to get at an appropriate solution of the case but also satisfies the family members to agree and look at the actual intention of the deceased testator.