diff --git a/lib/spack/spack/solver/asp.py b/lib/spack/spack/solver/asp.py
index 23e7141497b..6ba9111e941 100644
--- a/lib/spack/spack/solver/asp.py
+++ b/lib/spack/spack/solver/asp.py
@@ -806,6 +806,8 @@ def visit(node):
         self.control.load(os.path.join(parent_dir, "concretize.lp"))
         self.control.load(os.path.join(parent_dir, "os_compatibility.lp"))
         self.control.load(os.path.join(parent_dir, "display.lp"))
+        if spack.error.debug:
+            self.control.load(os.path.join(parent_dir, "causation.lp"))
         timer.stop("load")
 
         # Grounding is the first step in the solve -- it turns our facts
diff --git a/lib/spack/spack/solver/concretize.lp b/lib/spack/spack/solver/concretize.lp
index 24cff31cc85..470137070e0 100644
--- a/lib/spack/spack/solver/concretize.lp
+++ b/lib/spack/spack/solver/concretize.lp
@@ -48,6 +48,13 @@ error(100, multiple_values_error, Attribute, Package)
      attr_single_value(Attribute),
      2 { attr(Attribute, Package, Version) }.
 
+%-----------------------------------------------------------------------------
+% Define functions for error handling
+%-----------------------------------------------------------------------------
+
+#defined error/9.
+#defined condition_cause/2.
+
 %-----------------------------------------------------------------------------
 % Version semantics
 %-----------------------------------------------------------------------------
@@ -86,17 +93,6 @@ version_satisfies(Package, Constraint, HashVersion) :- version_satisfies(Package
 { attr("version", Package, Version) : version_declared(Package, Version) }
  :- attr("node", Package).
 
-% error we expect users to see
-error(0, "Version '{0}' of {1} does not satisfy '@{2}'", Version, Package, Constraint, startcauses, VersionCause, ConstraintCause)
- :- attr("node", Package),
-    attr("version", Package, Version),
-    imposed_constraint(VersionCause, "node_version_satisfies", Package, Version),
-    condition_holds(VersionCause),
-    attr("node_version_satisfies", Package, Constraint),
-    imposed_constraint(ConstraintCause, "node_version_satisfies", Package, Constraint),
-    condition_holds(ConstraintCause),
-    not version_satisfies(Package, Constraint, Version).
-
 % Error to ensure structure of the program is not violated
 error(2, "No version from '{0}' satisfies '@{1}' and '@{2}'", Package, Version1, Version2)
   :- attr("node", Package),
@@ -108,17 +104,6 @@ error(2, "No versions available for package '{0}'", Package)
   :- attr("node", Package), not attr("version", Package, _).
 
 % A virtual package may or may not have a version, but never has more than one
-% Error to catch how it happens
-error(0, "Version '{0}' of {1} does not satisfy '@{2}'", Version, Virtual, Constraint, startcauses, VersionCause, ConstraintCause)
- :- attr("virtual_node", Virtual),
-    attr("version", Virtual, Version),
-    imposed_constraint(VersionCause, "node_version_satisfies", Virtual, Version),
-    condition_holds(VersionCause),
-    attr("node_version_satisfies", Virtual, Constraint),
-    imposed_constraint(ConstraintCause, "node_version_satisfies", Virtual, Constraint),
-    condition_holds(ConstraintCause),
-    not version_satisfies(Virtual, Constraint, Version).
-
 % fallback error for structure in case there's another way for it to happen
 error(100, "Cannot select a single version for virtual '{0}'", Virtual)
   :- attr("virtual_node", Virtual),
@@ -173,15 +158,6 @@ possible_version_weight(Package, Weight)
   :- attr("node_version_satisfies", Package, Constraint),
      version_satisfies(Package, Constraint, _).
 
-% More specific error message if the version cannot satisfy some constraint
-% Otherwise covered by `no_version_error` and `versions_conflict_error`.
-error(0, "No valid version for '{0}' satisfies '@{1}'", Package, Constraint, startcauses, ConstraintCause)
-  :- attr("node_version_satisfies", Package, Constraint),
-     imposed_constraint(ConstraintCause, "node_version_satisfies", Package, Constraint),
-     condition_holds(ConstraintCause),
-     C = #count{ Version : attr("version", Package, Version), version_satisfies(Package, Constraint, Version)},
-     C < 1.
-
 % Error for structure of program
 error(10, "Cannot satisfy '{0}@{1}'", Package, Constraint)
   :- attr("node_version_satisfies", Package, Constraint),
@@ -234,28 +210,6 @@ attr(Name, A1, A2, A3, A4) :- impose(ID), imposed_constraint(ID, Name, A1, A2, A
    not imposed_constraint(Hash, "node_flag", Package, FlagType, Flag),
    internal_error("imposed hash without imposing all flag values").
 
-% associated conditions by cause -> effect
-condition_cause(Effect, Cause) :-
-  condition_holds(Effect), condition_holds(Cause),
-  attr(Name, A1),
-  condition_requirement(Effect, Name, A1),
-  imposed_constraint(Cause, Name, A1).
-condition_cause(Effect, Cause) :-
-  condition_holds(Effect), condition_holds(Cause),
-  attr(Name, A1, A2),
-  condition_requirement(Effect, Name, A1, A2),
-  imposed_constraint(Cause, Name, A1, A2).
-condition_cause(Effect, Cause) :-
-  condition_holds(Effect), condition_holds(Cause),
-  attr(Name, A1, A2, A3),
-  condition_requirement(Effect, Name, A1, A2, A3),
-  imposed_constraint(Cause, Name, A1, A2, A3).
-condition_cause(Effect, Cause) :-
-  condition_holds(Effect), condition_holds(Cause),
-  attr(Name, A1, A2, A3, A4),
-  condition_requirement(Effect, Name, A1, A2, A3, A4),
-  imposed_constraint(Cause, Name, A1, A2, A3, A4).
-
 #defined condition/2.
 #defined condition_requirement/3.
 #defined condition_requirement/4.
@@ -613,19 +567,6 @@ attr("variant_value", Package, Variant, Value) :-
     variant(Package, Variant),
     build(Package).
 
-error(0, "'{0}' required multiple values for single-valued variant '{1}'\n    Requested 'Spec({1}={2})' and 'Spec({1}={3})'", Package, Variant, Value1, Value2, startcauses, Cause1, Cause2)
-  :- attr("node", Package),
-     variant(Package, Variant),
-     variant_single_value(Package, Variant),
-     build(Package),
-     attr("variant_value", Package, Variant, Value1),
-     imposed_constraint(Cause1, "variant_set", Package, Variant, Value1),
-     condition_holds(Cause1),
-     attr("variant_value", Package, Variant, Value2),
-     imposed_constraint(Cause2, "variant_set", Package, Variant, Value2),
-     condition_holds(Cause2),
-     Value1 < Value2. % see[1]
-
 error(100, "'{0}' required multiple values for single-valued variant '{1}'", Package, Variant)
   :- attr("node", Package),
      variant(Package, Variant),