Aliant Inc. v. Ellph.com Solutions Inc., 2012 NSCA 89 deals with security for costs. In so doing the Court undertook an extensive examination of the exercise of judicial discretion and its intersection with the boundaries of appellate review. An analytical framework was provided to explain how, during the decision-making process, the judge is performing several functions with the result that certain aspects of the judge’s decision will attract different standards of review on appeal:
 Justice Moir’s order was discretionary, interlocutory, and had no terminating effect on the litigation. For reasons I will explain in a moment, the sole issue before the motions judge was fairness.
 The standard of review in matters such as this is well settled. We will only intervene if we are persuaded that wrong principles of law have been applied, or that failing to intervene would produce an obvious injustice. The threshold for overturning a discretionary order is considerable and is not easily displaced. As this Court said in A.B. v. Bragg Communications, 2011 NSCA 26 (CanLII), 2011 NSCA 26:
 … Clear error of law or a substantial injustice must be established. …
 … appellate courts are restrained in choosing to intervene. Absent an error in law or a manifest injustice we will decline to do so. The threshold for seeking reversal is high. It is not a soft or casual target. Any party seeking to set aside an interlocutory discretionary order has a heavy onus. Litigants should be reminded that it is not a burden which will be satisfied easily. …
 Thus, in the absence of a clear error of law or a substantial injustice we will refuse to intervene. Appeals from interlocutory matters create delay, run up costs for the parties, and tie up the court’s own resources while other proceedings in the system wait to be tried. A judge hearing motions in Chambers develops a well-honed proficiency in the exercise of discretion, especially in cases where he or she has heard the witnesses being examined first hand. These are some of the reasons why the standard of review is strictly applied where any party attempts to set aside a discretionary, interlocutory order.
 In its written and oral submissions Aliant confined itself to complaints that the motions judge had erred in principle in refusing to order the respondents to put up security for costs. In other words, Aliant does not rely upon the second branch of the test, which would invite our intervention so as to prevent a patent injustice. Consequently, this appeal is limited to alleged flaws in the judge’s decision which Aliant says amount to errors in law.
 As will become apparent, the thrust of Aliant’s appeal in this case is based on the assertion that the motions judge erred in principle by the way in which he considered (or ignored) the appellant’s interests when ultimately refusing to order security for costs. Given the appellant’s arguments I want to address what is meant by the concepts, “error in principle” and “exercise of discretion”. For it is an examination of that discretion and its intersection with the boundaries of appellate review that lie at the heart of this appeal.
 The case law is replete with examples of judicial efforts to describe what is meant by the phrase “error in principle”. Justice Chipman of this Court provided oft-quoted guidance in Minkoff v. Poole 1991 CanLII 2516 (NS CA), (1991), 101 N.S.R. (2d) 143, where at ¶ 10-11 he set out the rule governing appellate review of interlocutory discretionary orders:
At the outset, it is proper to remind ourselves that this Court will not interfere with a discretionary order, especially an interlocutory one such as this, unless wrong principles of law have been applied or a patent injustice would result. …
Under these headings of wrong principles of law and patent injustice an
 We see similar pronouncements in countless other cases. See for example: Haldorson v. Coquitlam (City), 2000 BCCA 484 (CanLII), 2000 BCCA 484; Pike v. Cook,  O.J. No. 4529 (
 In Friends of Oldman River Society v. Canada (Minister of Transport), 1992 CanLII 110 (SCC),  1 S.C.R. 3, the Supreme Court of Canada at ¶ 104 cited the following statement of Viscount Simon L.C. in Charles Osenton & Co. v. Johnston,  A.C. 130 at 138,  2 All E.R. 245 (H.L.) as accurately describing the principles governing appellate review of a lower court’s exercise of discretion:
The law as to the reversal by a court of appeal of an order made by the judge below in the exercise of his discretion is well-established, and any difficulty that arises is due only to the application of well-settled principles in an individual case. The appellate tribunal is not at liberty merely to substitute its own exercise of discretion for the discretion already exercised by the judge. In other words, appellate authorities ought not to reverse the order merely because they would themselves have exercised the original discretion, had it attached to them, in a different way. But if the appellate tribunal reaches the clear conclusion that there has been a wrongful exercise of discretion in that no weight, or no sufficient weight, has been given to relevant considerations such as those urged before us by the appellant, then the reversal of the order on appeal may be justified. [underlining mine]
 From these and similar authorities we know that appellate intervention may be justified when important factors are ignored, or irrelevant factors emphasized; or when no or insufficient weight is given to relevant considerations. While such principles may be easily expressed, the difficulty lies in their application.
 Not much ink has been spilled attempting to explain how these concepts come to be applied whenever a trial judge’s well recognized discretion to weigh the evidence (“accept some, none, or all”) and decide the facts, is challenged on the basis of the very weight assigned to that evidence by the judge who heard the case. In the face of settled law which has consistently held that “provided the discretion is exercised within acceptable limits, and not arbitrarily, this court will not interfere” (see for example, Sharpe v. Wakefield et al.,  A.C. 173; MacIsaac v. MacIsaac,  N.S.J. No. 185 (C.A.) at ¶ 18) a reasonably informed observer could not be criticized for asking – what is left of a trial judge’s discretion if it can be disturbed so easily on appeal? The issues raised in this case provide an opportunity to respond to that and similar questions.
 For example, how do these juridical pronouncements from the past, which attempted to define the scope of appellate review, play out in the real world? What is their practical application in today’s legal discourse such that when appellate intervention is required, the result will not seem arbitrary, but rather one which promotes consistency and predictability and offers precedential guidance? To me the answer lies in recognizing that certain aspects of the judge’s decision on appeal will attract different standards of review. This is the starting point in conceptualizing the analytical framework to be applied when discretionary orders are the subject of appellate review.
 Let me begin by discussing the judge’s role when faced with a motion such as this. In hearing the evidence and then deliberating to arrive at an outcome, the judge is performing several functions. First, the judge must identify and apply the proper legal test. This was a motion brought by Aliant seeking an order requiring the plaintiffs to put up security for costs. Thus, the motions judge was obliged to apply the proper legal test relevant to such a motion. This first step is a question of law, reviewable on a standard of correctness. In this part of the analysis the judge must be right. No deference is owed. Let me use a simple example to illustrate my point. Suppose the judge borrowed a principle from the legal test on a motion for a stay of proceedings, and required the moving party to prove irreparable harm before obliging the plaintiffs to post security for costs. Clearly, importing such a foreign legal concept into a security for costs case would constitute an error in principle, warranting our intervention.
 The second function performed by the motions judge will be to identify the relevant factors or criteria which ought to be considered when applying the legal test to the evidence adduced. In order to identify the appropriate criteria the judge will look to the jurisprudence, statutes, rules or other basis of authority in order to identify the list of factors which ought to be taken into account. The judge will also consider the cause of action, the pleadings, and the factual and legal matrix between the parties. This examination will entail a consideration of matters that raise questions of both fact and law, but with a decided legal primacy, to be tested on a correctness standard. In this case, Moir, J. looked to the “broad discretion” given him under CPR 42.01, the circumstances giving rise to the litigation, as well as the legal principles established in cases here and in other provinces to formulate a list of factors he considered to be relevant in disposing of the motion. These factors included: the sequence of steps and rebuttal presumptions set out in the Rule; the comparative financial resources of the parties; whether corporate artifice extended insulation from costs; access to justice; delay; the nature of the business relationship between these parties; impecuniosity and whether the cause of action may have led to it; the reality surrounding this corporate “shell-dom”, all of which were to be considered under the overarching criterion of fairness between the parties. Here again the motions judge would have to be right in identifying the appropriate factors engaged by the legal test applicable to a security for costs motion. I will use another simple example to illustrate my point. Suppose the judge included as a factor, the tidy, more attractive appearance of the moving parties’ factum when deciding the motion in their favour. Clearly such a criterion would be completely irrelevant. Its application would amount to error in principle, warranting appellate intervention. From this we see that selecting the appropriate factors in the application of the legal test to be satisfied on the motion, is also a matter of law, reviewable on a correctness standard.
 Having identified and applied the proper legal test, and chosen the relevant factors to be considered, the judge’s last function is to evaluate those factors in order to arrive at a just result. This evaluation has two parts: First the judge will decide the relative importance of each of the factors. This will involve prioritizing them in some fashion in a way that ranks or assigns differing weights to each criterion. Once that is done the remaining part of the judge’s analysis will involve a balancing of those factors, as if they were inscribed in a ledger or placed on a scale, to resolve at the end of the analysis whether the calculus of those factors favours one party, or the other. It is in this part of the analysis that the judge’s discretion is recognized. Having seen the witnesses, heard the evidence and counsel firsthand the judge is best positioned to decide the weight that ought to be accorded those factors which are relevant to the motion before the court. This is where appellate courts recognize the wide latitude accorded trial judges in the exercise of their discretion. This Court explained the rationale for such a deferential approach in A.B. (Litigation Guardian of) v. Bragg Communications Inc., 2011 NSCA 26 (CanLII), 2011 NSCA 26 at ¶ 31-33.
 And so, when we say that we may well intervene in “… cases where no weight or insufficient weight has been given to relevant circumstances” (Minkoff, supra), this does not mean that we are free to substitute our own exercise of discretion, for the discretion already exercised by the judge, or choose to intervene simply because we would have weighted the factors differently had we been hearing the motion. We ought not concern ourselves with the minutiae of how the judge ranked or prioritized the level of importance for each of the factors taken into account. That process, that exercise is not one in which we should engage. Rather, the question we ought to ask – having regard to the wide latitude granted trial judges in exercising their discretion – is whether the weight attached to the relevant factors is sufficient to satisfy the legal test engaged by the motion before the court.
 Again let me use a simple example to illustrate my point. Suppose there are five factors to be considered when applying the legal test to decide the motion. I will refer to them as A, B, C, D and E. If, in assessing those factors, the judge decides that the proper weight to be attached to them is A(15), B(5), C(35), D(25) and E(20), it is not our role to disturb the judge’s order simply because we would have attached greater or lesser importance to those same factors.
 To summarize to this point, selecting the factors that will be relevant to the analysis involves an assessment of the circumstances, the cause of action and the legal and factual matrix that joins the parties. It will require an examination of matters that raise questions of both fact and law but which are primarily focussed on issues grounded in law, and will therefore be reviewable on a correctness standard. Accordingly, in constructing the list of relevant factors, the judge must be right.