Any person of full age and sound mind may dispose, by will, of all his property except what is sufficient to pay his debts, or what is allowed as a homestead, or otherwise given by law as privileged property to his wife and family. [§3522.] The validity of a will depends upon the mental capacity of a testator and the fact that he was uninfluenced in making the disposition of his property. If it appears that the testator was incapable of exercising discretion and sound judgment and of fully realizing the effect and consequences of the will, though he may not be absolutely insane, he will not be in such mental condition that he can make a legal will. If he is of weak mind and it appears that he was imposed upon or unduly influenced, such facts will invalidate the will. A testator having testamentary capacity may dispose of his property in any manner, and to any person he may choose, and may deprive his heirs of any share in his estate, without any explanation or any express declaration of disinheritance. The fact that a will is unjust and unreasonable, in the absence of proof of undue influence, or insufficient capacity, will not render the will void. [Sidenote: Subsequent property.] Property to be subsequently acquired may be devised when the intention is clear and explicit. [§3523.] If the intention to convey property acquired after the execution of the will is apparent or may be inferred from a fair construction of the language used, it will be sufficient, although the intention may not be directly expressed. [Sidenote: Verbal wills.] Personal property to the value of three hundred dollars may be bequeathed by a verbal will, if witnessed by two competent witnesses. [§3524.] [Sidenote: Soldier or mariner.] A soldier in actual service, or a mariner at sea, may dispose of all his personal estate by a will so made and witnessed. [§3525.] [Sidenote: In writing. Witnessed. Signed.] All other wills, to be valid, must be in writing, witnessed by two competent witnesses and signed by the testator, or by some other person in his presence and by his express direction. [§3526.] It is necessary that the witnesses shall subscribe the will, but not that they shall have any knowledge of its contents, nor that they shall see the testator sign it. It is sufficient if the signature is adopted or acknowledged in their presence. If a will is made with the intention of disposing of real property it must be executed according to the requirements of the laws of the state where the real property is situated. [Sidenote: Interest of witness.] No subscribing witness to any will can derive any benefit therefrom, unless there be two disinterested and competent witnesses to the same. [§3527.] But if, without a will, he would be entitled to any portion of the testator's estate, he may still receive such portion to the extent in value of the amount devised. [§3528.] [Sidenote: Revocation.]