statute--of "common employment" in the law of employers' liability; see _Smith_ v. _Baker_, 1891, A.C. 325. Other maxims deal with rights of property--_Qui prior est tempore, potior est jure_ (Co. _Litt._ 14 a), which consecrates the position of the _beati possidentes_ alike in municipal and in international law; _Sic utere tuo ut alienum non laedas_ (9 Co. _Rep._ 59), which has played its part in the determination of the rights of adjacent owners; and _Domus sua cuique est tutissimum refugium_ (5 Co. _Rep._ 92)--"a man's house is his castle," a doctrine which has imposed limitations on the rights of execution creditors (see EXECUTION). In the laws of family relations there are the maxims _Consensus non concubitus facit matrimonium_ (Co. _Litt._ 33 a)--the canon law of Europe prior to the council of Trent, and still law in Scotland, though modified by legislation in England; and _Pater is est quem nuptiae demonstrant_ (see Co. _Litt._ 7 b), on which, in most civilized countries, the presumption of legitimacy depends. In the interpretation of written instruments, the maxim _Noscitur a sociis_ (3 _Term Reports_, 87), which proclaims the importance of the context, still applies. So do the rules _Expressio unius est exclusio alterius_ (Co. _Litt._ 210 a), and _Contemporanea expositio est optima et fortissima in lege_ (2 Co. _Inst._ 11), which lets in evidence of contemporaneous user as an aid to the interpretation of statutes or documents; see _Van Diemen's Land Co._ v. _Table Cape Marine Board_, 1906, A.C. 92, 98. We may conclude this sketch with a miscellaneous summary: _Caveat emptor_ (Hob. 99)--"let the purchaser beware"; _Qui facit per alium facile per se_, which affirms the principal's liability for the acts of his agent; _Ignorantia juris neminem excusat_, on which rests the ordinary citizen's obligation to know the law; and _Vigilantibus non dormientibus jura subveniunt_ (2 Co. _Inst._ 690), one of the maxims in accordance with which courts of equity administer relief. Among other "maxims of equity" come the rules that "he that seeks equity must do equity," i.e. must act fairly, and that "equity looks upon that as done which ought to be done"--a principle from which the "conversion" into money of land directed to be sold, and of money directed to be invested in the purchase of land, is derived.