Meaning: Where there is the same reason, there is the same law; and of things similar, the judgment is similar.
For the first part of this maxim it may be said, that law is founded upon reason, and is the perfection thereof, and that what is contrary to reason is contrary to law ; and for the second, that where no established precedent can be found exactly in point, whereupon to ground a decision, the case in question may be properly decided by reference to similar cases. The law will not admit any presumption against reason ; for the law is reason and equity ; to do right to all and to keep men from wrong and mischief ; and therefore the law will never make any construction against law, equity, and right. Wherever there is the like reason there is the like law, for, “ Ratio est anima legis.” And therefore, “ Ratio potest allegare deficiente lege;” but it must be, “ Ratio vera et legalis, et non apparens.” So, “ Argumentum a simili,” is good in law ; “ sed, similitudo legalis est casuum diversorum inter se collatorum similis ratio, quod in uno similium valet, valebit in altera, dissimilium dissimilis est ratio.”
“Nihil quod est contra rationem est licitum.” For reason is the life of the law, and the common law is nothing but reason, and this reason is that which has been gotten by long experience, and not each man's natural reason. So it is said that this legal reason is “summa ratio;” for, if all the reason that is in men's heads were united into one, yet could he not make such a law as is the law of England.' Because, by many succeeding ages, it has been fined and refined by an infinite number of grave and learned men and by long experience grown to such perfection as to justify the old rule, “ Neminem oportet esse sapientorem legibus”. No man ought to be wiser than the law, which is the perfection of reason.
If a man have power to grant an estate in fee simple he has power to demise the same estate for a term of 1000 years, or any less estate than the fee, and that for the like reason that as he has power over the fee which is the greatest estate, he has power over any less estate.
All cases of construction and intention are governed by this rule ; as, where the terms of a deed are difficult to be understood, they are construed by reference to other like cases. And, as where the words of a will are in themselves at variance, the intention of the testator is considered in order to reconcile them. So, also, one clause in an instrument is looked at to find out the construction to be put upon another clause in the same instrument, and a man's acts at one time are looked to as guides to an opinion to be formed of his acts at another.
The preamble of an Act of Parliament is looked to as a guide to the construction of the Act itself, and as containing the reason for the enactment, and so one act of the Legislature is looked to as a guide in the construction of another. One circumstance is considered to induce another like circumstance, and all reasonable consequences, and so in similar cases. All argument under this maxim may be said to be a priori, or from cause to effect ; as, when murder is imputed to any one having a hatred to the deceased, and an interest in his death ; in this case his guilt being admitted, his hatred and interest serve as a motive and to account for the commission of the crime.