causeless

Having no obvious cause; fortuitous or inexplicable.

Groundless or unreasonable.

[H]e […] by his overcarefulneſſe and cauſeleſſe ſuſpicion, deprived himſelf of this benefit, and implunged himſelf in much juſt hatred for his unjuſt dealing and treachery.

Alas my fears are cauſless, and ungrounded, / Fantaſtick dreams, and melancholick fumes / Of crazy ſtomacks, and diſtempered brains: / Has this convinc'd you?