Samuel Clarke: Causality versus Design

"For to say a thing is produced, and yet that there is no cause at all of that production, is to say that something is effected, when it is effected by nothing; that is, at the same time when it is not effected at all.—Whatever exists, has a cause, a reason, a ground of its existence; (a foundation, on which its existence relies; a ground or reason why it doth exist rather than not exist;) either in the necessity of its own nature, and then it must have been of itself eternal; or in the will of some other being, and then that other being must, at least in the order of nature and causality, have existed before it" (Samuel Clarke).

Naturalists might argue that things in the cosmos have a cause, but were not designed. Yes, that's possible logically but how probable is it that all things in the cosmos and the cosmos itself were not designed? Again, it's logically possible that Biltmore House was not made by intelligent designers or that it did not have human builders, but how likely is it?