_if the sun
shine the day will be clear_, there is no certainty of _the sun shining_.
Of the two propositions one only embodies a certain fact, and that is
certain only conditionally.

Now an action, wherein there enters any notion of uncertainty, or
indefinitude, and is at the same time connected with another action, is
expressed, not by the indicative mood, but by the subjunctive. _If the sun_
shine (not _shines_) _the day will be clear._

Simple uncertainty will not constitute a subjunctive construction,--_I am_,
perhaps, _in the wrong_.

Neither will simple connection.--_I am wrong_, because _you are right_.

But, the two combined constitute the construction in question,--_if I _be_
wrong, you are right_.

Now, a conjunction that connects two certain propositions may be said to
govern an indicative mood.

And a conjunction that connects an uncertain proposition with a certain
one, may be said to govern a subjunctive mood.

_The government of mood is the only form of government of which
conjunctions are capable._

s. 506. Previous to the question of the government of conjunctions in the
way of mood, it is necessary to notice certain points of agreement between
them and the relative pronouns; inasmuch as, in many cases, the relative
pronoun exerts the same government, in the way of determining the mood of
the verb, as the conjunction.

Between the relative pronouns and conjunctions in general there is this
point of connection,--both join propositions. Wherever there is a relative,
there is a second proposition. So there is wherever there is a conjunction.

Between certain relative pronouns and those particular conjunctions that
govern a subjunctive mood there is also a point of connection. Both suggest
an element of uncertainty or indefinitude. This the relative pronouns do,
through the logical elements common to them and to the interrogatives:
these latter essentially suggesting the idea of doubt. Wherever the person,
or thing, connected with an action, and expressed by a relative is
indefinite, there is room for the use of a subjunctive mood. Thus--"he that
troubled you shall bear his judgment, _whosoever_ he _be_."

s. 507. By considering the nature of such words as _when_, their origin as
relatives on the one hand, and their conjunctional character on the other
hand, we are prepared for finding a relative element in words like _till_,
_until_, _before_, _as long as_, &c. These can all be expanded into