Taxonomy of Determinism and Indeterminism (source: History of the Free Will Problem, @ informationphilosopher.com)

According to Wikipedia,

Determinism is the general philosophical thesis that states that for everything that happens there are conditions such that, given them, nothing else could happen. (...)

Determinism is also the name of a broader philosophical view, which conjectures that every type of event, including human cognition (behaviour, decision, and action) is causally determined by previous events.

In philosophical arguments, the concept of determinism in the domain of human action is often contrasted with free will. The argument called indeterminism (otherwise "nondeterminism") negates deterministic causality as a factor and opposes the deterministic argument.

Determinists believe any determined system is fully governed by causal laws resulting in only one possible state at any point in time.

-- Wikipedia > Determinism

OTOH, we find in Aristotle a clear distinction between three types of causation:

1. Necessity (Greek ἀνάγκη, ananchê): deterministic causality or, simply determinism.

2. Chance (Greek τύχη, tychê ): indeterministic causality or, simply indeterminism.

3. Agency of a free agent: what Aristotle says depends "on us" (ἐφ' ἡμῖν, eph'êmin  ).

Agent causation is therefore a "third thing" (tertium quid), beyond necessity and chance, that causes events or chains of events.

Aristotle clearly affirms the distinction between chance and necessity:

Nor is there any definite cause for an accident, but only chance (τυχόν), namely an indefinite (ἀόριστον) cause. (Metaphysics, Book V, 1025a25)

It is obvious that there are principles and causes which are generable and destructible apart from the actual processes of generation and destruction; for if this is not true, everything will be of necessity: that is, if there must necessarily be some cause, other than accidental, of that which is generated and destroyed. Will this be, or not? Yes, if this happens; otherwise not. (Metaphysics, Book VI, 1027a29)

He also clearly affirms the notion of agency and of free agent: 

But if it is manifest that a man is the author of his own actions, and if we are unable to trace our conduct back to any other origins than those within ourselves, then actions of which the origins are within us, themselves depend upon us, and are voluntary. (Nicomachean Ethics, III, v, 6, Loeb translation)

But it is Epicurus (born 43 years after Aristotle) who summarized this triple classification of causality in the clearest and most essential way:

... some things happen of necessity, others by chance, others through our own agency [Greek: παρ’ ἡμᾶς (par'êmas), literally "by us"]. ... necessity destroys responsibility and chance is inconstant [Greek: ἄστατος (astatos): also unstable, uncertain]; whereas our own actions are autonomous, and it is to them that praise and blame naturally attach. (Epicurus, Letter to Menoeceus [§133], @ epicurus.net - bold by MdS)

This clear affirmation of agent causation and free will is surprising to most people, who are not familiar with Epicurus' own thought directly, but rather with its "vulgate" by the Latin poet Lucretius (see On the Nature of Things, 2.251-262, 289-293, @ perseus.tufts.edu)

In spite of Aristotle's and Epicurus' early and clear affirmation of agent causation and free will, most of the following philosophical thought seems to consider only the extreme positions of Determinism (an consequent incompatibilism) and Indeterminism (and consequent a-causalism).

This is a recent comment by Bob Doyle ("scientist, inventor, and philosopher") on the state of the problem:

Why have most philosophers been unable for millenia to see that the common sense view of human freedom is correct? It is partly because their logic and language preoccupation likes to say that either determinism or indeterminism is true, and the other must be false.

Determinism and indeterminism are the horns of the dilemma presented as the standard argument against free will, which we can trace back unchanged to the earliest discussions of freedom, determinism, and moral responsibility.

Our physical world includes both, though the determinism we have is only an adequate description for large objects. So any intelligible explanation for free will must include both a limited indeterminism and an adequate determinism, in a temporal sequence that creates information.

(History of the Free Will Problem, @ informationphilosopher.com)

I believe that Doyle's approach may well be the closest we have to an explanation of agent causation and free will (between the two "horns" of Determinism and indeterminism) that is consistent with philosophy, science and also theology.